Lake Ronkonkoma Clean Lake Study Update

Transcription

Lake Ronkonkoma
Clean Lakes Study Update
Lake Ronkonkoma
Clean Lake Study Update
Town of Brookhaven
Suffolk County, Long Island, New York
One Independence Hill
Farmingville, New York 11738
BROOKHAVEN TOWN BOARD
Brian X. Foley, Supervisor
Timothy Mazzei, Councilman
Steve Fiore-Rosenfeld, Councilman
Kathleen A. Walsh, Councilwoman
Connie Kepert, Councilwoman
Jane Bonner, Councilwoman
Keith Romaine, Councilman
June 2008
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Lake Ronkonkoma
TABLE OF CONTENTS
Page
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Introduction
Goals of the 1986 Study & Accomplishments
Summary of Current Issues
3.1 Stormwater
3.2 Land Use
3.3 Bacterial Monitoring & Wildfowl Populations
3.4 Shoreline Erosion
3.5 Lake Level & Flooding
3.5.1 Sources of Water to the Lake System
Current Conditions & Analysis
4.1 Sources of Information
4.2 Watershed Area
4.3 Groundwater
4.4 Lake Level
4.5 Smithtown Drainage
4.6 Water Budget
4.7 Precipitation
4.8 Stormwater Runoff
4.9 Stormwater Runoff Basin Descriptions
4.10 Resident Canada Geese
4.11 Land Use
4.12 Zoning
Relevant Programs & Studies
5.1 Programs
5.2 Preparation of a TMDL
Water Quality
6.1 Source Water Assessment Program
6.2 Water Quality
6.3 Current Water Quality Monitoring
6.4 Surface Water Quality Data
6.4.1 Cyanotoxin Monitoring
6.4.2 SCDHS Bathing Beach Monitoring
6.4.3 USGS Monitoring
6.4.4 NYSDEC Monitoring
6.5 Groundwater Quality Data
6.5.1 Suffolk County Observation Wells
6.5.2 USGS Observation Wells
Recommendations
1
3
6
6
7
8
9
9
9
13
13
13
14
15
20
21
22
24
25
26
30
30
32
32
34
37
37
37
38
38
38
40
42
43
44
44
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46
FIGURES
APPENDICES
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FIGURES
Figure 1-1
Figure 1-2
Figure 1-3
Figure 3-1
Figure 3-2
Figure 3-3
Figure 3-4
Figure 4-1
Figure 4-2
Figure 4-3
Figure 4-4
Figure 4-5
Figure 6-1
Municipal Boundaries
Groundwater Table and Divide of 1984 (USGS) in the
Greater Central Suffolk County Region
2004 Aerial Photograph with Drainage Area, Primary
Drainage Area, Lake and Ponds
Land Use and Recommended Land Use from 1986
Zoning and Recommended Zoning from 1986
Public & Civic Owned Properties
Publicly & Privately Owned Lake Front Properties
Lake Ronkonkoma Topography from USGS Digital
Elevation Model
Topography with a Hill Shading Effect
Primary Drainage Area & Sub-drainage Areas
Stormwater Basins, Structures & Ponds
Source Water Assessment Program Capture Zones near
Lake Ronkonkoma
Water Quality Sampling Locations
TABLES
Table 4-1
Table 4-2
Table 6-1
Table 6-2
Table 6-3
Table 6-4
Long-Term Monthly Precipitation
Summary of Precipitation Data since 1949 by Month
Bathing Beach Data Summary
Number of Beach Closure Days
Sample of USGS Water Quality Data Parameters
USGS Groundwater Data Summary
Page
22
23
40
41
42
44
CHARTS
Chart 4-1
Chart 6-1
Appendix A
Appendix B
Appendix B-1
Appendix B-2
Appendix B-3
Appendix C-1
Appendix C-2
Total Precipitation by year (1949-2006)
Summary of Lake Ronkonkoma Bathing Beach Closures 1988-2007
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41
APPENDICES
Results from Stormwater Runoff/Pollutant Loading Analysis for the Primary Drainage Areas
Waterbody Information
303(d) Waterbody List
March 2001 PWL Assessment for Lake Ronkonkoma
February 2006 PWL Assessment for Lake Ronkonkoma
Summary Sheets- Water Quality Data for Lake Ronkonkoma 1988-2007
Data Sets & RIBS Data
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Lake Ronkonkoma
1.0
INTRODUCTION
In 1986, a management plan for Lake Ronkonkoma
was prepared through combined efforts of several
agencies including the Suffolk County Planning
Department, Suffolk County Health Department and
the New York State Department of Environmental
Conservation (NYSDEC).1
The primary purpose of the 1986 Clean Lakes Study
(hereafter referenced as the “1986 Study”) was to
develop a comprehensive management plan for Lake
Ronkonkoma and its watershed area. The management
plan included provisions for the protection and
enhancement of the lake's water quality and use, and
protection of the lake shoreline and the publicly owned
lands that surround the lake.
This current study, commissioned by the Town of
Brookhaven, provides an update of the 1986 Study to
provide an account of those tasks that have been accomplished since 1986 and presents future
opportunities for improvement of Lake Ronkonkoma and its watershed area.
Figure 1-1 illustrates the location of the Town and Village boundaries near Lake
Ronkonkoma. The lake is located in central Suffolk County, Long Island, New York. Lake
Ronkonkoma is within the Town of Islip. The Town of Islip controls the southwest shoreline
of the lake and a small part of the watershed southwest of the lake. The Town of Smithtown
adjoins the northwest shorelines of the lake and includes the watershed area northwest of the
lake including the Great Bog. The Town of Brookhaven adjoins the east side of Lake
Ronkonkoma and the largest part of the watershed area east of the lake. The Village of Lake
Grove does not border Lake Ronkonkoma, but is within the watershed area northeast of the
lake.
Lake Ronkonkoma is the largest lake in Suffolk County, classified as a glacial kettlehole. The
lake system, which includes Lake Ronkonkoma as well as the Great Bog located to the north of
the lake is a groundwater fed system (though it does receive stormwater) and has no streams
which enter or leave the system. The community around the lake is largely developed with
residential use of medium density (2 to 10 dwelling units/acre) but also is home to multi-family
residential, commercial, institutional and recreational uses. Various areas around the lake that
are now residential in use, were once part of the lake system; however, the areas were filled
and developed with homes starting in the 1930s when County Road (CR) 16 was first built.
1
The Lake Ronkonkoma Clean Lakes Study - 1986 was financed in part with Federal funds from the United
States Environmental Protection Agency under Grant COO0433.
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Lake Ronkonkoma
The lake system was historically a popular recreational area, but in recent decades has been
susceptible to water quality problems, including algae blooms, presence of cyanobacteria, low
dissolved oxygen and suspected presence of pathogens. The lake beaches have been closed to
swimming for periods ranging from a few days to the entire season because of high bacteria
counts at the bathing beaches and the continual presence of wildfowl.
Flooding in the area is now a primary concern for those residents whose homes were built in
high water table areas proximate to the lake and bog. The lake system water level responds to
both precipitation and groundwater levels (water table elevation); during various years (1979,
1984, 2005-2008) water table and lake elevations have caused basement, road and property
flooding. Figure 1-2 provides a contour map of the water table in central Suffolk County
along with the 1984 groundwater divide. Although both the groundwater table elevation and
the precise location of the groundwater divide vary with time; the lake system and its drainage
area has always been located south of the groundwater divide2, meaning that groundwater in
the vicinity of the lake generally flows to the south. Figure 1-3 provides a 2004 aerial
photograph of Lake Ronkonkoma, the Great Bog to the north, and the drainage area that makes
up the study area for this report.
The 1986 Study included an analysis of the physical and biological processes, characteristics
and resources of the lake and the immediate watershed area. Geology, topography, hydrology
and land use activities were also discussed. This inventory provides an update of earlier
information where available using current technology which allows the generation of up-todate resource maps utilizing Geographic Information Systems (GIS) software. The lake and
surrounding area has been inventoried using GIS mapping techniques and field work. In
addition, GIS has been used to define drainage watersheds delineated based upon surface
topography (using digital elevation models) and these watershed have been refined based upon
field observations, locations of roadways and other impervious surfaces that effect drainage
patterns, recharge features and other drainage infrastructure.
The basic intent of this study is to provide an update of information available since the 1986
Study was completed, as well as to track the implementation of recommendations of the 1986
Study where possible. The project has involved coordination with the Towns of Brookhaven,
Smithtown, Islip, Suffolk County Department of Health Services (SCDHS), Suffolk County
Department of Public Works (SCDPW), the United States Geological Survey (USGS) and the
New York State Department of Environmental Conservation (NYSDEC). Information from
each of these agencies as well as from the United States Fish and Wildlife Service (USF&W)
and Cornell Cooperative Extension were incorporated into this study to gain an understanding
of existing conditions and management options. In addition, this study includes public input
received through meetings with a task force assembled by the Town of Brookhaven to focus on
issues involving the lake. Outreach with local groups has been used to obtain local insight, tap
the knowledge of those intimately familiar with the lake and its resources and to gain public
acceptance for the Lake Ronkonkoma Clean Lakes Study Update.
2
Since the collection of data regarding groundwater began in the 1940s.
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2.0
GOALS OF THE 1986 STUDY & ACCOMPLISHMENTS
The 1986 Study was completed as a combined effort between the Suffolk County Planning
Department, Suffolk County Department of Health Services and the New York State
Department of Environmental Conservation.
The 1986 Study identified the following problems:
•
•
•
•
•
•
•
Harmful bacteria (affecting lake activities)
Algae blooms (indicating a potential imbalance in the ecosystem)
Elevated phosphorus levels
Elevated nitrogen loading
Incompatible land use
Degraded shoreline
Illegal dumping
The 1986 Study identified stormwater runoff as a primary source of pollution and conveyance
mechanism for nutrient loads, and included a Management Plan with many recommendations
to achieve water quality improvements. The following provides a list of the general goals and
recommended actions from the 1986 Study and some of the accomplishments that have been
achieved since the time the study was prepared.
1986 Goals
Reduce the existing bacterial
loadings to the lake.
Whenever possible, reduce
existing nutrient loads to the
lake.
Accomplishments
Due to improvements in stormwater collection in the Town of
Brookhaven and along the County Road system, it is expected that
less direct stormwater runoff currently reaches the lake system than
in 1986; however, it is noted that since there has also been an
increase in impervious surfaces in the area. Site plan and
subdivision review of land use applications in the Towns and Village
do include (and in the past have included) provisions to require all
stormwater to be contained on new development sites within the
engineering design criteria of the municipality.
The implementation of the NYS DEC Phase II Stormwater program
requirements in 2003, has resulted in an increased awareness of the
impacts of stormwater runoff and accordingly, construction and post
construction measures are enforced. In addition, water quantity and
water quality requirements have resulted in increased detention and
treatment. In 2008, NYSDEC adopted a further change in the
program further enhancing stormwater management at the Town
level. This program will be discussed further in other sections of
this report.
No data exists on changes to the use of fertilizer and turf
management methods; however, outreach regarding the impacts of
misuse of fertilizer is ongoing.
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The Town of Brookhaven installed sediment basins in drains
surrounding the lake as a pilot project, which includes the Storm
Basin cartridge filtering device to remove pollutants.
An on-going program to discourage the resident goose population
has been established through the Lake Ronkonkoma Chamber of
Commerce.
Customized curb markers have been designed and printed;
eventually 400 markers will be attached to each County maintained
storm drain indicating that the drain discharges directly to the lake
(the design is specific to Lake Ronkonkoma). The program started
in the spring of 2006 and according to the SC Annual Stormwater
Report is currently ongoing.
Signs advising the public not to feed the waterfowl were installed at
the Town of Brookhaven beach in 2005.
Prevent any future increases in
nutrient, sediment or bacterial
loads to the lake. Prevent any
new intensive land uses.
A majority of land acquisition recommendations were accomplished.
However, a few new homes were constructed adjacent to the lake in
Islip Town on parcels suggested for acquisition in the 1986 Study.
Some of the accomplishments listed above also assist in meeting this
goal.
Prevent future illegal sanitary
or other waste disposal into or
adjacent to the lake.
Some problems (from flooded single family septic systems) have
been documented since the 1986 Study. In addition, the Bavarian
Inn was closed due to flooding and it is expected that its sanitary
system does not have adequate leaching due to the high
groundwater/lake level. This property has since been approved for
acquisition by Suffolk County.
The Phase II program includes a minimum control measure
requiring the detection of illicit discharges to surface waters.
Townships are implementing stormwater programs to meet this and
other measures.
Improve the stormwater
drainage systems within the
immediate lake watershed
area. Prevent any future manmade erosion of the lake
shoreline.
Many changes to recharge and detention basins have been
accomplished; final work at the Town of Brookhaven Beach park is
complete; the proposed construction of a drainage basin adjacent to
the Town of Brookhaven beach has been bid for construction.
To date, this study update has not identified the implementation of
any specific measures to prevent erosion of the shoreline.
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Lake Ronkonkoma
Acquire additional properties
required to complete the park
system.
Additional properties were acquired as recommended. The trailer
park property, located in the Smithtown part of the lake watershed,
is owned by Suffolk County and the majority of units are being
removed from the parkland.
Prevent any man-made
conditions that would increase
the flooding problems
associated with a rise in lake
levels.
An opportunity exists related to the diversion of stormwater
currently discharged from the Town of Smithtown into the north end
of the Great Bog to a different recharge basin (owned by Suffolk
County); this opportunity is currently being explored by the
Smithtown Town Engineer.
The 1986 Study provides an excellent baseline of lake conditions and management
recommendations. The implementation of recommendations since 1986 provides incremental
benefit to the lake though measurement of benefits is difficult and water quality concerns
persist. The next section summarizes current issues for renewed focus and updated
management recommendations.
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Lake Ronkonkoma
3.0
SUMMARY OF CURRENT ISSUES
The water quality of Lake Ronkonkoma and the Great Bog is affected by numerous factors.
The 1986 Study identified stormwater runoff, land use, and nuisance wildlife as the largest
contributors to pollution in the lake. These factors affecting water quality have not changed
dramatically in the past 22 years. Consistent with the 1986 Study, the following factors remain
the most critical influences in water quality of Lake Ronkonkoma.
3.1
Stormwater
Many of the recommended changes to recharge and detention basins have been accomplished,
including several improvements accomplished by Suffolk County. In addition, improvements
at the Brookhaven Town Beach have been completed, including a modified parking area with
stormwater detention and improved access to the lake. The construction of a drainage basin
adjacent to the Town of Brookhaven beach is pending. In addition, NP&V conducted a storm
survey following record rainfall events in October 2005 and identified direct stormwater inputs
to the lake. In most areas it was reported that stormwater was contained by local recharge
basins and catchment devices in the streets.
In recent years, both the USEPA and NYSDEC have focused efforts on implementing
regulations aimed at controlling pollutants that are discharged in stormwater runoff. These
regulations, commonly known as Stormwater Phase II, were established in 2003 and updated
in May 2008, and require that general permits for stormwater discharges from Municipal
Separate Storm Sewer Systems (MS4s) and for construction activities disturbing one or more
acres. Under these regulations, construction sites with one or more acre of disturbance are
required to obtain permit coverage under the NYSDEC General Permit for Stormwater
Discharges from Construction Activities. To qualify for coverage under the permit, an erosion
control plan and stormwater pollution prevention plan must be prepared and implemented at
the site. Weekly inspections of the erosion control measures and elements of the drainage
system installed at the construction sites are also required. The permit is intended to reduce
stormwater runoff and sediment from entering surface water bodies during construction
activities. The Town of Brookhaven is a regulated MS4 under this program and has developed
a Stormwater Management Program in accordance with the NYSDEC regulations. The
Stormwater Management Program includes the development of public outreach programs on
stormwater impacts, evaluation of best management practices for municipal operations (i.e.,
road salting, street sweeping, roadway drainage design, etc.), mapping of existing stormwater
outfalls and drainage features, and establishing a program for review of construction sites for
proper erosion controls and stormwater containment and local implementation of the
construction stormwater permits.
The changes made according to the NYSDEC General Stormwater Permit requirements are
expected to result in reduced stormwater runoff from new construction as well as increased
education and outreach efforts related to the impacts of stormwater runoff. The County has
implemented a program which involves the installation of curb markers at all County
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Lake Ronkonkoma
maintained stormwater drains to alert the public of the direct connection to the lake. More than
400 drains in the Lake Ronkonkoma watershed area are slated for the markers. Suffolk County
now has a stormwater education program through Cornell University Cooperative Extension of
Suffolk County as part of the Suffolk County Stormwater Management Program. Further
information can be obtained at www.co.suffolk.ny.us/stormwater/ed_outreach.html. The
County provides educational programs to schools and groups interested in the topic which
includes a 20 minute Power Point presentation. A DVD for teachers is also available through
this office (www.co.suffolk.ny.us/stormwater/schoolPresentations.html).
The Town of Brookhaven has also increased public outreach efforts and has conducted a pilot
program for the use of stormwater filtration devices. In addition, the Town has improved
standard operating procedures for the documentation of maintenance of their stormwater
systems including routine clean up and upkeep of stormwater conveyance installations as is
reported in their 2006 annual Stormwater report.3 The Town of Brookhaven has also
completed the inventory and mapping of all stormwater basins and conveyances of stormwater
within the Town’s contributing area.
3.2
Land Use and Zoning
Although progress has been made in the areas of land acquisition and stormwater abatement,
there are still land use and stormwater challenges. There have been multiple changes in land use
(including infill of residential properties) and there remain several inappropriate land uses
directly adjacent to the lake system. Figure 3-1 illustrates the recommended land use from the
1986 Study this is also compared with current land use4. The two graphics contained in Figure
3-1 illustrate different land uses in the study area as compared to the recommended land uses
from the 1986 Study. This figure shows how new development that has occurred since 1986
varies from the recommendations from 1986 Study. 5 Figure 3-2 illustrates the recommended
zoning from the 1986 Study as compared to current zoning classifications.
In comparing census information, the 2000 population within the Lake Ronkonkoma drainage
area was 13,927 persons, an increase of approximately 100 (0.7%) since 1990. This increase is
not as significant as the countywide increase that occurred during this period of 1.2%. The small
increase in growth accounts for the increase in developed residential properties in the study area
since 1986. Today, very few vacant parcels of land exist which are not owned by public
agencies. Figure 3-3 illustrates the public and civic owned properties (generally homeowners
3
The Town of Islip and Town of Smithtown do not mention stormwater minimum control measures specific to
the Lake Ronkonkoma watershed area in their 2006 Annual Reports.
4
Land use is identified by the 3-digit tax assessor’s code and labeled with the colors used by the Suffolk County
Department of Planning. Some modifications have been made based upon field observations to more accurately
reflect current land use.
5
It is noted that the Bavarian Inn property was recognized as a commercial property in 1986, as it is today.
However, the property has been recently approved for purchase by the County for public use. It is not known at
this time if the County plans to redevelop the site or remove the improvements to create parkland.
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Lake Ronkonkoma
association’s access properties) within the watershed area and Figure 3-4 illustrates the publicly
and privately owned lakefront properties. The majority of privately owned properties on the
lakefront are developed with single family homes or businesses. In a few cases, the properties
are vacant and are owned by Homeowner’s Associations to provide lake access.
3.3
Bacterial Monitoring and Wildfowl Populations
Wildfowl management and bacteria remain issues of concern with respect to water quality and
recreational usage of Lake Ronkonkoma. The Town of Islip Beach was frequently closed to
swimming during the summers of 2005 thru 2007. The Town of Brookhaven Beach remained
closed for the entirety of 2006 and 2007.
It is noted that in 2004, the SCDHS changed the indicator bacteria used for the determination
of beach closures. Prior to 2004, SCDHS monitored total coliform (TC) and fecal coliform
(FC) as indicators for beach closures. TC are a closely related bacteria and FC are a subgroup
of total coliforms which occur in the intestines of warm blooded animals and therefore may be
used to indicate an unsafe level of fecal contamination. In 2004, following recommendations
from the United States Environmental Protection Agency (USEPA), SCDHS began monitoring
Escherichia coli (commonly known as E. coli), a specific species of FC bacteria, and
Enterococci (another group of bacteria unrelated to coliforms but also occurring in the
intestines of warm blooded animals). These indicators were found to be better indicators in
correlating swimming related gastrointestinal illness as compared with TC or FC. The County
noted that this change in procedure may have contributed to more closure days at Lake
Ronkonkoma. Regardless of the protocol change, it is expected that the Town beaches would
still have experienced a high rate of closure due to the presence of a large population of
resident Canada Geese.
The resident Canada Geese population has greatly increased in recent years, resulting in
problems with water quality and aesthetics. The Town of Brookhaven Beach has not been
opened for swimming since 2005 due to the high bacterial levels associated with the fecal
matter from the waterfowl population. As the geese largely congregate just above the lake’s
waterline, the addition of stormwater drainage infrastructure does not solve the waterfowl
problem. There is a need to control the resident Canada Geese population and discourage
nesting in the lake system area.
Civic organizations have attempted to dissuade the resident geese population through humane
means (such as the use of dogs and egg oiling) and have had some success; although not
enough to solve the problem. It is important to note that resident Canada Geese have up to a
20-year lifespan and generally return to the area of their original nesting site to nest on a yearly
basis. Therefore, control of this population will require a long term, consistent program.
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Lake Ronkonkoma
3.4
Shoreline Erosion
The lake shoreline continues to be subject to erosion in several areas, particularly along Lake
Shore Road on the east side of the lake. In addition, since the initiation of this study, the lake
level has been unnaturally high, which is expected to result in further deterioration of the
shoreline in areas where the water level has not typically reached the embankment such as on
the west side of the lake. Unfortunately, due to a lack of baseline survey information, there is
no way to assess the degree of erosion that has occurred since the 1986 Study. The Town may
wish to conduct a survey of the properties along the lake to monitor change in the future.
3.5
Lake Level & Flooding
Flooding affects the quality of life for area residents, particularly those residences located east
of the Great Bog. In addition, the water quality of the lake may be affected by flooding as a
result of sanitary systems and transport of loose material on the roads and lawns to the lake
without filtering or uptake of nutrients (i.e. pet waste, sanitary systems, fertilizers, etc.).
The water level of the lake is a function of both rainfall and groundwater elevation. The
conditions in the past three years illustrate how high quantities of precipitation and high
groundwater results in elevated lake levels and flooding problems. Homes and business
located on the north and northeast portion of the lake/bog system and especially those within
the primary drainage area (see yellow boundary on Figure 1-3) can be expected to have
basement flooding problems during times of high groundwater levels. High groundwater and
resultant flooding in this area corresponds to high rainfall during winter months (Steenhuis,
T.S. et al., 1985). Some homes built during times of low groundwater levels (the mid-1960s
drought) have also had problems with basement flooding. This condition was also reported in
the 1986 Study, which specifically notes that during a drought in the 1960’s, inappropriate
development occurred in areas with normally high groundwater. These homes are now
experiencing flooding problems, some that are so problematic to make the home uninhabitable
(and in one case leading to purchase of a home on Charles Court by the County of Suffolk).
The 1986 Study indicated previous plans for dealing with the extraordinarily high lake level,
including the diversion of stormwater from Smithtown to other recharge areas and other more
expensive measures such as pumping to the Connetquot River. However, following the
publication of the 1986 Study, the lake level receded and the need for such remedies was no
longer considered a priority for governmental organizations, particularly in view of the cost
and engineering logistics of these solutions.
3.5.1 Sources of Water to the Lake System
Precipitation, stormwater runoff and groundwater inflow are source of water to the lake and
bob. In addition to rainfall falling within the drainage area of the lake system, the Great Bog
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Lake Ronkonkoma
also receives a volume of water from outside the natural drainage area. The Town of
Smithtown has three recharge basins to the north of the lake system (on Nichols Road,
Cornelia Lane and Browns Road)6, which would otherwise be outside of the drainage area of
the lake and bog. The Town of Smithtown recharge basins do not percolate, and since the
1970s, the Town has pumped water from this area into the Great Bog. The following graphic
illustration was included in the 1986 Study and illustrates sources of water to Lake
Ronkonkoma, including the pumped volumes from the abovementioned recharge basins.
Another factor in area flooding problems is the presence of a clay layer – known as the
“Smithtown Clay” (Krulikas, R.K. and Koszalka, E.J., 1983) located within the upper glacial
water table aquifer. Its presence slows the infiltration of groundwater to the aquifers below
and slows the recharge of stormwater runoff in recharge basins and can contribute to localized
high water table values during years of high rainfall.
Since 2005, the lake levels have been high, which is consistent with the unusually high
groundwater elevation and the high levels that have occurred in the past, including in 1979 and
1984. Flooding from high groundwater elevations is a problem that is pervasive in areas with
shallow depth to groundwater across the island; however, it is exacerbated in this area by the
presence of the Smithtown Clay. The following graphic illustrates areas in the vicinity of Lake
Ronkonkoma which have a similar ground elevation (depicted in various color shades); this
figure was constructed using GIS and the USGS Digital Elevation Model for the area. The
water surface of Lake Ronkonkoma is approximately 17 meters (55.8’) above mean sea level.
6
These three recharge basins are interconnected by a system of gravity piping and discharge via a pump station
and force main into the Great Bog. It is noted that this graphic illustrates the general groundwater contributory
area from the 1986 Study.
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Lake Ronkonkoma
Lake Ronkonkoma
The following graphic illustration includes an overlay of the year 2000 water table map on the
above topographic elevation map. The data points indicate the groundwater elevations used to
create the water table contour map. It is noted that the nearest groundwater elevation to the
lake (circled) is depicted to be 50.5’ or 15.4 meters.
Lake Ronkonkoma
Finally, the following graphic illustration has been prepared to indicate locations where the
ground surface elevation and the top of the water table are within 10 feet (about 3 meters) of
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Lake Ronkonkoma
each other and would therefore be subject to flooding in a period when the groundwater table is
high.
Lake Ronkonkoma
Areas in pink are expected to have problems with water drainage in times of high groundwater levels.
The areas of high groundwater and potential flooding cover a large area surrounding the lake
and in low elevation/high groundwater areas proximate to the lake. This information is useful
to identify areas of concern for potential mitigation and also to identify areas where further
development should be precluded.
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Lake Ronkonkoma
4.0
4.1
CURRENT CONDITIONS & ANALYSIS
Sources of Information
GIS databases were collected from the three townships (Brookhaven, Islip and Smithtown),
Suffolk County Real Property and Suffolk County Department of Public Works. These
databases are comprised of shapefiles and personal geodatabases, both consistent with ESRI’s
ARCGIS 9.2 program. GIS shapefiles have been created for the Village of Lake Grove by
NP&V for parts of the Village within the study area and for spatially based features to include
in the analysis contained herein. Water quality data was collected from various agencies and
from public sources, including a SUNY professor (Dr. Christopher Gobler) who completed a
report on levels of cyanotoxins in Suffolk County lakes in 2007. Significant input was
received through contact with personnel at many agencies including the Town of Brookhaven,
USGS, Cornell Cooperative Extension, NYSDEC and SCDHS and SCDPW, as well as
through contact with local organizations and elected officials.
4.2
Watershed Area
The study area was determined to be the area where stormwater runoff could, within reason,
directly discharge to the lake7. The surface water drainage area for Lake Ronkonkoma is
generally the area surrounding the lake that is delineated by topography, i.e. lands that slope
towards Lake Ronkonkoma. The study area was created using USGS digital topographic data
(USGS digital elevation models, or DEMs) and modified to include some areas where
infrastructure has been established which redirects stormwater to the lake that would not
otherwise drain into the lake. Figure 4-1 illustrates the local topography which generally
defines the study area; Figure 4-2 illustrates the topography with a hill shading effect applied
which gives a visually enhanced illustration of the topography near the lake. It is noted that
many areas within the overall Lake Ronkonkoma drainage area have stormwater runoff which
drains to recharge basins or local ponds rather than directly into the lake.
Sub drainage areas were also delineated by digital hydrologic analysis using GIS and the
DEMs for this area.8 It was recognized that some of the watershed area designated by the 1986
7
Suffolk County Real Property department has GIS data for every tax parcel in the county. A license agreement
was obtained from Suffolk County Real Property and GIS parcel databases were obtained from the three
townships (Brookhaven, Islip and Smithtown) as well as from the SCDPW. These data are comprised of
shapefiles and personal geodatabases, all files recognized by ESRI’s ARCGIS 9.1 software. Additional GIS
shapefiles were created for the Village of Lake Grove within the study area. In addition, shapefiles for spatially
based features were created by NP&V as part of this study for use in the analysis.
8
The GIS software used for this analysis was ESRI’s ArcView, along with the hydrology extension for ArcView
Spatial Analyst (http://www.esri.com/news/arcuser/arcuser498/hydrology.html). This software uses the
discretized surface of the earth along with the elevation estimate for each discretized unit to delineate watersheds
(drainage areas) and their discharge locations (pour points).
Page 13
Lake Ronkonkoma
Study would not naturally drain into the lake (when strictly using the criteria of elevation to
determine the watershed areas). That is because man-made structures (like roadway drainage
systems) can alter the true watershed area; as a result, the study area was altered to include
these areas. For the purpose of this study, the drainage area encompasses the entire 1986
watershed area as well as the additional drainage area identified using the USGS DEMs. In
addition, a primary drainage area is defined, which encompasses the area with similar
elevations as the water level of the lake and bog. This primary drainage area is illustrated on
Figure 1-3 and Figures 4-1 through 4-4 as a single polygon in the center of the study area
which include the lake and bog, and surrounding lands. Based upon the results of digital
hydrologic modeling, the primary drainage area ranges in elevation from 17 meters to
approximately 20 meters (or 56 to 66 feet) above mean sea level. The primary drainage area in
general, is the destination for stormwater runoff for the rest of the study area (stormwater
runoff that does not infiltrate or become directed to a recharge basin or pond). The land within
the primary drainage area is especially critical to the health of the lake; it has a relatively low
depth to groundwater thus making infiltration of rainwater less likely and rainfall on these
areas is more likely to be directed to the surface water of the lake or bog without the benefit of
filtering, and therefore promotes conveyance for pollutants, sediments and debris.
The primary and sub drainage areas delineated using the digital elevation model (and edited to
include some man-made stormwater infrastructures) are illustrated on Figure 4-3. Stormwater
recharge basins and ponds are shown in Figure 4-4, special treatment basins (where
stormwater is detained before entering the lake or bog) are shown on Figure 4-5.
4.3
Groundwater
The local water table is between 45 feet and 55 feet above mean sea level (USGS, 1983). The
topography (from USGS digital elevation model measured in the early 1990s) indicates the
lake level for Lake Ronkonkoma to be 17 meters (±56 feet) above mean sea level. There is
very little difference between the lake elevation and the water table elevation from these
general indicators; Lake Ronkonkoma is a groundwater-connected lake that also receives
substantial runoff. As a result, groundwater moves to and from the lake through the lake
bottom sediments as a function of the stage of the lake as compared with the water table. The
elevation value of 55 feet above mean sea level for an upper glacial well measured by SCDHS
in 2004 (S47718) near the lake is also very close to the estimated lake level of 56 feet (above
mean sea level). Bathymetry of the lake from 1983 indicates that Lake Ronkonkoma is up to
20 meters (66 feet) deep (in a small area located near the southern end of the lake) and is more
typically 4 or more meters deep (≥13 feet deep). This would put the bottom of the lake well
into the water table.
The 1986 Study assumed groundwater influence on the lake from groundwater upgradient of
the lake as is illustrated in the graphic on page 10 (that is, having a higher water table elevation
than the area and generally in the direction of the groundwater divide for the upper glacial
aquifer) in a triangular pattern.
Page 14
Lake Ronkonkoma
The Source Water Assessment Program (SWAP, CDM, 2003) results indicate that the
groundwater flow regimes near the lake are much more complicated than originally assumed.
Figure 4-5 illustrates a portion of the capture zones found in the Source Water Assessment
Program near Lake Ronkonkoma. This is significant for two reasons: (1) capture zone
geometry differs from the even ovals orientated between the groundwater divide and the south
shore, the ovals are distorted by the influence of the lake and are more rounded for shorter
capture periods (indicating less regional groundwater influence and more capture of recently
recharged water); and (2) the capture zone for SCWA’s well #S-77010 (50 years and older) is
situated in Lake Ronkonkoma and the bog (indicating that lake water eventually is withdrawn
by this public water supply well field).9
In general, the following statements may be made based upon the foregoing data:
1. During high groundwater years, groundwater contributes to the volume of the lake.
2. During low groundwater years, the lake water contributes to the groundwater during periods of
precipitation when the lake responds and achieves a higher elevation that the water table.
3. The water quality of the lake effects groundwater quality and visa versa.
4. The lake effects shallow and deep groundwater flow patterns.
5. Some lake water may eventually be withdrawn for water supply purposes as SCWA continues
use of Well S-77010 (or installs a proximate well which includes Lake Ronkonkoma in its
capture zone). The travel time for water from Lake Ronkonkoma to reach the well is over 50
years.
4.4
Lake Level
The lake level is a reflection of the water table and at the time of preparation of this report
(2007/2008), the groundwater table was at an all time high10. The USGS has indicated that
real-time continuous monitoring could provide a better understanding of the interaction
between the lake level and water table elevation. The following summarizes information that
currently exists regarding the lake level:
• The lake system and entire study area are south of the groundwater divide.
• The local water table is in the range of 55’ above msl. The lake level is in the same range.
9
It is noted that there is a caveat to consider when reviewing the SWAP results as the SWAP modeling assumes
steady-state conditions. Because the lake and the shallow groundwater are hydraulically connected and the lake is
easily influenced by rainfall conditions (and because the study area scale is different then the scale considered for
the SWAP modeling), a steady-state condition is not an entirely valid assumption. (Collecting current and
historical observations for transient ground water modeling for a study near Lake Ronkonkoma would be required
to consider performing a transient groundwater flow model and more data on the Smithtown Clay would also be
required).
10
Since the collection of data regarding groundwater began in the 1940s.
Page 15
Lake Ronkonkoma
• This indicates that the lake is a surface reflection of the water table. However, since the lake
receives surface runoff from a large drainage area, during times of high precipitation and high
lake levels, the lake is expected to recharge the aquifer. During low lake level periods, the
aquifer is the lake level. This groundwater inflow-outflow relationship is a dynamic hydrologic
condition.
During the period of this study, the lake level was at a historically high elevations. This is a
problem that is seen across the island; however, in the case of Lake Ronkonkoma, the
condition is exacerbated by the presence of the Smithtown Clay layer.
The Smithtown Clay is a layer within the soils observed and documented by Krulikas and
Koszalka, 1983 (USGS Water Resources Investigations Report, WRI No. 82-4075,
http://pubs.er.usgs.gov/usgspubs/wri/wri824075) that exists near the land surface and has a
lower permeability than the surrounding soils. This inhibits downward infiltration of
precipitation and can cause saturated soils above the clay layer (even if soils below the clay
layer are unsaturated). Several maps were published by Krulikas and Kozalka including
Figures 3 and 4 in the publication, partial reprints of which are presented in the following
graphic.
Figure 3: Thickness of clay unit
Source: Krulikas and Koszalka, 1983
Page 16
Lake Ronkonkoma
The preceding graphic is Figure 3 – Thickness of clay unit from the Krulikas and Koszalka
report. It illustrates equal lines of thickness of the clay unit and the inferred limit of the clay
based upon the limited data collected for this purpose. Note: Lake Ronkonkoma is a small
circle in the Ronkonkoma terminal moraine located in the center of both figures (arrow added
by NP&V).
Figure 4: Altitude of top of clay unit
The graphic above is Figure 4 – Altitude of top of clay unit, from the Krulikas and Koszalka
report. (Larger scale views of these maps for the areas around Lake Ronkonkoma are included
on the following pages).
The conclusions that may be reached from these figures with respect to Lake Ronkonkoma are
as follows:
1. The clay unit exists beneath at least the north part of Lake Ronkonkoma but is likely to
diminish and eventually not exist at the southern end of the lake.
2. The clay may be 50 feet thick or more at the north end of the lake.
Page 17
Lake Ronkonkoma
3. These maps indicate that there were only 3 data values (borings) near Lake Ronkonkoma used
to determine the top of the clay and the thickness of the clay.
4. The land surface elevation around the lake (see Figure 2-1) is generally about 20 meters or 66
feet above msl, which is only slightly greater than the 61 feet listed as the top of clay for the
data point nearest the lake.
5. The presence of the clay at the north end of the lake and absence at the south end of the lake
may explain why the bog is located at the north end and not the south end of the lake, and why
the recharge basin near the Brookhaven Town Park (across the street, and at the south end of
the lake) is dry and so many other basins (and ponds) around the lake (generally to the north)
contain water year-round.
Large Scale Figure 3 (portion) - Thickness of clay unit
Page 18
Lake Ronkonkoma
Large Scale Figure 4 (portion) - Altitude of top of clay unit
It has been theorized by members of the community that the lake water no longer recharges to
groundwater and that the bottom of the lake has over time become silted or otherwise
“plugged” and therefore is contributing to flooding. This is likely a misconception which is
not supported by data or hydrologic principles. During years when the groundwater elevation
is high, the lake level is correspondingly high. During years when groundwater levels are
lower, the lake level is lower. This is evidence that the lake is a reflection of the groundwater
table. During periods of high precipitation and corresponding runoff within the Lake
Ronkonkoma watershed, the lake contributes to the groundwater until there is an equilibrium
between the lake and groundwater.
The Lake Ronkonkoma task force has requested that funding be provided for core sampling to
understand whether siltation of the lake bottom is reducing recharge to groundwater. The more
likely conclusion and one supported by hydrologic data and principles is that the lake is not
“clogged” and that the flooding in the area is due to high precipitation (particularly during nongrowing seasons), resulting in high groundwater and lake water elevations. It is not a
recommendation of this report that funding be provided to collect bottom core samples since
this data would not be expected to provide valuable information. While the results may
indicate poor soils for leaching, the lake transmits water at all levels dependent upon where the
groundwater elevation is at any given time. Rather, continuous monitoring of lake level,
Page 19
Lake Ronkonkoma
groundwater elevation, volume from Smithtown pumping and precipitation events is required
if the lake dynamics are to be completely understood.
It is expected that the level of the lake related to precipitation events can only be controlled by
reducing the amount of water that enters the lake. This would not remedy high lake elevations
caused by regional high groundwater. Expensive and logistically difficult measures such as
dewatering of the regional groundwater system are not viewed as viable on their own;
however, multiple benefits could potentially be gained by sewering, provided that a suitable
discharge location and adequate funding are available. Sewage Treatment Plants (STPs) are
known to reduce groundwater elevations through conveyance of wastewater to a treatment
facility which discharges to marine waters or an alternative location with suitable depth to
groundwater. An STP for the Lake Ronkonkoma area would result in less nitrogen-bearing
discharge to groundwater and would permit greater land use densities to be achieved.
Currently, Article 6 of the Suffolk County Sanitary Code (SCSC) limits land use density to
protect groundwater from elevated nitrogen concentrations. A part of the Lake Ronkonkoma
community’s vision is increased land use density in the downtown area (to the east of the lake).
A regional STP to sewer the Lake Ronkonkoma area would be a monumental public works
project requiring governmental commitment from three (3) townships and Suffolk County, a
sponsoring entity (most logically Suffolk County) and a very large investment. A feasibility
study for such a project could be considered to test viability and to establish preliminary cost
projections and engineering solutions.
Another approach to relieving high lake levels is to redirect stormwater to recharge basing
outside the area of Smithtown Clay. Studies to locate gravel lenses in this area would be
expensive, however, if pursued and found, a recharge basin located over a gravel lens would
likely succeed in alleviation of flooding and high water levels for a proximate area.
4.5
Smithtown Drainage
As noted in Section 3.5.1, the Town of Smithtown diverts stormwater from three recharge
basins north of the natural drainage area for the lake system into the Great Bog (these recharge
basins do not percolate, and since 1979, the Town has pumped water from these locations into
the Great Bog). The water consists of stormwater runoff from Browns Road and other
contributing roadways as well as groundwater. While not a significant volume in the context
of the entire lake/bog volume, any increase in volume under the current extreme conditions is
worth examination. For a relative view of the quantity of water that is pumped into the bog,
NP&V evaluated pumping rates provided by the Town of Smithtown, estimated based upon
electricity utilized by the pump. While an accurate daily estimate is not possible, it was
determined that the highest estimated volume amounts to less than 0.001 of the total volume of
the lake.
In 2007, the Smithtown Engineering Department had been successful in redirecting a portion
of the recharge water to another basin; however, this location is also inside area underlain by
Page 20
Lake Ronkonkoma
the Smithtown Clay. The pumping from the Town of Smithtown Browns Road basin into the
Great Bog is not ideal with respect to the goals for water quality and quantity in the Lake
Ronkonkoma system, particularly the wetlands associated with the Great Bog. It is, however,
not the major cause of either problem in the Lake. The major cause of flooding is elevated
groundwater levels (which also contribute to the amount of pumping needed from the Browns
Road basin). The redirection of stormwater effluent into the bog provides a benefit from the
standpoint that the bog provides an enhanced filter for treatment of this stormwater, and
directing stormwater to the Great Bog also enhances evapotranspiration as a result. This
practice may minimize the impact this stormwater has on the water quantity and quality of the
lake.
The Town of Smithtown should continue to explore opportunities for discharge in areas other
than the Great Bog particularly where effective groundwater recharge can be achieved (beyond
the Smithtown Clay).
4.6
Water Budget
The water budget for Lake Ronkonkoma was discussed in Chapter 5 of the 1986 Study. The
analysis contained in the 1986 Study had assumptions about the flux of water between the lake
and groundwater, which is difficult to estimate. The lake is a reflection of the groundwater
elevation; however, the volume of water in the lake and bog is also dependent upon other
factors, including water from precipitation, stormwater runoff, and direct pumping from
outside the drainage area (from the Smithtown recharge basin). Components necessary for
estimation of a water budget include long term temporal water level measurements as well as
groundwater elevation measurements for locations surrounding the lake and bog. It is noted
that Suffolk County wells installed for the 1986 Study were abandoned following the original
study and no water level information is available between 1986 and the present to allow for an
update of the water budget.
Change in water “storage” in the lake was assumed to be zero in the 1986 Study. Although
there are no measurements of the lake level available, anecdotal evidence indicates that the
lake level rose about six feet between October 2005 and October 2006. Since the surface area
of the lake is approximately 237 acres, and assuming the lake doesn’t increase in surface area
with a rise of elevation (a simplification for comparative purposes), additional storage in the
lake computes to be approximately 460 million gallons. Since the 1986 report assumed the
total volume of the lake to be 1,060 million gallons (approximately 1.1 billion gallons), this
anecdotally observed rise in lake level is equivalent to 43% of the total lake storage.
The assumption of no change in storage for Lake Ronkonkoma is not valid for the time span of
October 2005 to October 2006. This emphasizes the recommendation that regular
measurements of the lake level are needed. Since Lake Ronkonkoma and the Great Bog are an
interconnected system (with no surface water inflow or outflow), water level measurements
within the bog would also be useful (possibly near the Browns Road location where the
diverted stormwater runoff enters the bog).
Page 21
Lake Ronkonkoma
4.7
Precipitation
Precipitation determines the elevation of Lake Ronkonkoma as a function of water table
elevations and stormwater runoff which enters the lake. The BNL weather station at Upton,
NY is the nearest official weather station to Lake Ronkonkoma with long-term monitoring
data. The following table provides precipitation in inches per month from 1949 to 2007.
TABLE 4-1
LONG-TERM MONTHLY PRECIPITATION
Year
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
Jan
5.55
2.8
3.75
7.1
6.73
2.74
0.62
3.52
2.36
7.96
2.6
3.59
3.56
4.38
3.27
5.89
4.88
4.57
1.65
3
1.04
0.81
2.95
2.41
4.44
4.96
6.5
5.98
3.09
10.72
13.01
2.02
1.15
7.2
4.07
2.87
1.07
3.96
6.74
3.59
2.23
5.24
4.41
2.4
2.47
5.78
2.93
5.22
3.82
7.01
8.85
3.75
3.28
3.07
2.48
2.15
3.32
5.52
4.32
Feb
4.71
4.28
4.99
3.54
4.16
2.18
3.26
6.32
2.53
4.58
2.06
5.48
4.1
5.77
3.88
4.76
3.03
5.18
3.98
2.21
4.03
4.37
6.45
6.12
4.36
2.82
4.06
3.57
2.46
2.6
5.27
1.18
5.16
2.9
4.36
6.38
1.82
3.46
1.21
4.81
4.09
2.92
1.86
2.18
4.1
4.04
3.74
3.51
2.64
5.66
4.81
2.58
2.63
1.16
5.74
3.14
2.1
2.87
2.00
Mar
2.88
3.98
5.02
5.44
10.36
4.21
4.79
5.47
3.2
6.65
6.71
3.38
4.6
3.63
4.27
3.56
2.74
1.73
8.18
7.54
3.62
5.44
3.55
5.4
4.38
5.06
4.27
3.3
5.47
3.33
3.53
7.2
1.8
3.38
8.68
6.92
2.62
3.17
5.95
4.22
5.2
2.14
5.45
3.34
7.11
6.55
1.53
3.58
5.1
8.08
5.32
5.49
10.37
5.05
5.99
3.47
2.47
0.89
5.58
Apr
3.63
2.41
3.42
3.61
5.59
5.36
4.28
2.97
4.44
6.34
3.93
3.27
5.7
3.31
2.56
8.37
4.2
2.13
4.14
2
5.15
4.57
3.3
4.53
7.77
3.49
3.89
2.27
4.28
2.39
4.96
6.16
4.59
5.44
11.1
5.41
1.56
2.35
4.32
2.17
4.66
4.96
4.3
1.78
3.81
2.26
2.52
6.4
4.21
6.55
2.35
6.29
2.03
4.58
5.11
4.94
2.53
7.17
6.87
May
3.32
5.23
3.68
7.64
3.34
4.08
0.95
2.63
1.46
5.81
1.75
2.54
6.17
1.12
3.08
0.63
1.63
6.55
7.98
4.95
2.44
3.44
3.8
6.1
5.46
3.13
3.45
3.89
2.04
6.47
4.09
1.52
2.17
1.71
4.22
8.08
4.87
1.09
1.83
2.58
10.47
6.52
2.78
3.05
1.71
2.93
2.79
3.39
2.67
8.58
2.41
4.28
4.22
4.48
6.07
2.59
2.36
6.73
2.06
Jun
Trace
2.72
2.64
2.78
1.66
1.69
2.53
3
0.42
2.28
5.35
2.13
2.3
3.55
5.51
1.41
1.69
1.4
5.3
4.24
2.06
1.77
0.92
7.3
3.25
2.5
5.37
3.27
4.31
0.81
2.15
3.6
3.14
12.9
2.63
6.68
6.38
1.66
1.86
1.43
7.24
3.95
1.87
4.9
1.37
0.51
3.12
4.41
2.16
8.43
1.04
5.18
6.46
4.37
12.3
1.34
1.48
6.73
3.18
Jul
3.07
3.22
2.08
1
2.76
0.94
1.65
5.79
2.84
3.42
6.85
6.03
5.61
1.64
2.65
4.4
3.43
1.12
6.01
0.5
8.62
3.1
5.03
1.03
4.45
0.81
3.33
4.32
1.51
4.63
0.61
1.92
2.69
1.77
4.2
7.06
2.3
5.02
1.48
3.93
5.84
2.64
2.11
4.76
1.84
0.91
1.78
4.94
2.21
0.94
2.12
8.37
3.47
1.37
2.38
3.05
2.16
5.73
7.58
Aug
5.21
4.26
4.5
7.61
2.4
12
9.04
1.5
4.25
5.37
3.72
1.79
4.23
7.64
2.1
1.16
5.15
3.23
5.43
3.1
5.51
6.08
3.86
1.29
3.11
2.55
2.01
7.57
5.49
5.22
7.76
1.56
0.96
3.45
4.48
1.02
4.89
5.69
4.38
1.36
9.17
6.75
9.19
5.61
1.61
5.04
0.54
2.68
3.33
3.68
8.71
3.38
4.68
3.94
5.19
4.3
0.87
6.44
2.78
Sep
3.49
1.38
1.06
1.35
0.9
10.5
3.96
3.64
3.57
4.24
1.36
7.49
6.23
4.07
3.66
3.02
1.51
6.53
2.24
2.08
3.6
2.42
2.12
3.08
2.51
5.1
5.58
2.07
5.73
4.26
3.2
0.98
5.17
1.4
2.09
4.16
1.54
0.86
4.05
3.52
4.45
3.04
4.45
3.51
4.36
4.41
4.91
6.08
1.27
2.5
5.9
6.86
4.04
5.84
5.22
5.14
1.09
3.21
1.69
Oct
1.7
1.7
5.5
0.3
3.2
2.4
11
3
3.9
7.4
3.1
3.9
3.1
4.6
0.2
4.3
2.2
4.5
2.1
3
3.7
1.4
3.4
7.6
2.8
2.7
3.6
5.4
6.1
4.1
4.6
3.6
4.5
2.1
3.7
3.2
1.5
2.3
2.2
3.9
8.9
7.2
2.6
1.1
4.7
1.1
6
8.2
2.6
1.9
4.8
0.3
1
6.4
4.8
1.6
22
7.22
1.71
Nov
2.96
4.34
6.01
3.56
5.03
5.42
7.19
4.63
4.41
2.88
4.46
2.62
2.89
5.04
6.89
3.07
1.83
2.89
4
8.09
4.48
6.52
6.86
7.51
2.22
1.94
5.89
0.54
6.39
2.79
3.95
4.2
3.16
3.87
8.68
2.4
6.85
6.72
3.55
9.05
5.16
1.78
1.8
5.96
3.72
6.34
5.83
3.11
5.42
2.05
2.58
3.79
0.74
6.18
3.63
2.16
5
6.61
3.31
Dec
3.36
4.36
6.17
4.45
6.43
6.39
0.82
6.03
8.45
2.68
5.12
4.31
3.7
2.83
2.78
6.63
2.11
4.15
7.6
8.22
7.83
3.73
2.57
6.22
8
6.78
4.92
2.96
6.93
6.12
3.02
1.06
5.55
2.38
5.67
2.98
1.1
7.5
3.2
2.52
1.25
5.9
4.3
6.6
6.11
4.3
3.74
8.66
4.66
1.22
2.85
4.09
2.59
5.63
4.22
1.96
4.6
2.47
4.25
Total
36.56
36.31
42.63
43.94
46.1
51.51
49.7
42.42
33.34
56.92
41.92
42.26
48.45
44.77
38.05
40.56
32.24
39.78
51.02
40.72
44.24
39.93
42.25
52.41
44.74
35.02
47.96
42.2
46.89
47.33
53.1
33.93
34.48
46.04
58.17
54.18
35.43
36.23
37.59
40.53
67.41
47.11
40.83
38.56
36.79
39.86
35.66
51.56
35.38
55.39
48.87
50.28
45.55
52.07
63.11
35.86
50.12
61.59
45.33
Source: http://www.bnl.gov/weather/4cast/precip.html
Page 22
Lake Ronkonkoma
67.41
CHART 4-1
TOTAL PRECIPITATION BY YEAR (1949-2006)
35.86
45.33
50.12
55.39
48.87
50.28
45.55
52.07
51.56
47.11
40.83
38.56
36.79
39.86
35.66
35.38
54.18
33.93
34.48
35.43
36.23
37.59
40.53
46.04
46.89
47.33
42.2
47.96
53.1
52.41
44.74
40.72
44.24
39.93
42.25
39.78
38.05
40.56
44.77
41.92
42.26
42.42
48.45
51.51
49.7
51.02
56.92
35.02
35
32.24
40
33.34
45
42.63
43.94
46.1
55
36.56
36.31
Precipitation (inches/year)
60
50
58.17
65
61.59
63.11
70
19
4
19 9
51
19
5
19 3
55
19
5
19 7
5
19 9
6
19 1
6
19 3
65
19
6
19 7
69
19
7
19 1
7
19 3
75
19
7
19 7
79
19
8
19 1
8
19 3
8
19 5
8
19 7
89
19
9
19 1
93
19
9
19 5
9
19 7
99
20
0
20 1
03
20
0
20 5
07
30
Table 4-2 provides a summary of various data from the available long-term data. The long-term
average annual precipitation value is 48.72 inches per year.
TABLE 4-2
SUMMARY OF PRECIPITATION DATA SINCE 1949 BY MONTH
Year
Jan
Feb
Mar
Apr
May
Jun
Jul
4.16
3.77
4.80
4.32
3.85
3.56
3.34
Average
13.01 6.45 10.37 11.09 10.47 12.85
8.62
Maximum
0.62
1.16
1.56
0.63
0.42
0.50
Minimum
0.89
Source: BNL weather http://www.bnl.gov/weather/4cast/precip.html
Aug
4.40
11.98
0.54
Sep
3.62
10.47
0.86
Oct
4.03
22.14
0.18
Nov
4.43
9.05
0.54
Dec
4.53
8.66
0.82
Total
48.72
68.66
34.35
The above tables and chart illustrate the range of precipitation volume by year as well as
between consecutive months. The storm that occurred between October 13 and October 19
2005 (with the heaviest rainfall on October 15) was the largest storm ever recorded at Upton,
NY.11 The total rainfall that occurred for the month of October 2005 was by far the most
precipitation observed for any month since 1949.
11
"October 2005 was by far the wettest month in the last 58 years that the Lab has been keeping weather statistics, with
almost double the amount of rain recorded in any October, and easily beating the previous monthly 13.01 inches of record
rain in January 1979,” said Victor Cassella, a Brookhaven Lab meteorologist. “We received 17.23 inches of rain in five
consecutive days, from October 10 to 15, with 9 inches on October 14”. (Source: BNL Website).
Page 23
Lake Ronkonkoma
4.8
Stormwater Runoff
This report provides an updated assessment of
watersheds and sub-drainage areas and includes
pollutant load analysis for Lake Ronkonkoma.
Sub-drainage areas were calculated by digital
hydrologic analysis using GIS and the available
DEMs for this area. The GIS software used for
this analysis was ESRI’s ArcView, along with the
hydrology extension for ArcView Spatial
Analyst.12 This software uses the discretized
surface of the earth along with the elevation
estimate for each discretized unit to delineate
watersheds (drainage areas) and their discharge
locations (pour points). For this study, some of the
watershed area designated by the 1986 Study did not drain into the lake (when strictly using
the criteria of elevation to determine the watershed areas). Because man-made structures (like
roadway drainage systems) can alter the true watershed area, the study area (drainage area for
the purpose of this study) was altered to include all of the 1986 watershed area as well as the
drainage area calculated from digital elevation models. Review of Figure 4-1 indicates that
the lake and the Great Bog area to the north (as well as a few small ponds) are all within one
large polygon in the center of the study area. For the purpose of this study, this area has been
referred to as the primary drainage area. The primary drainage area is the lower elevation
area proximate to the lake as determined by the results of the digital hydrologic modeling that
designates the watersheds. This area ranges in elevation from 17 meters to about 20 meters
above mean sea level and is the area that is, in general, the destination for stormwater runoff
for the rest of the study area (stormwater runoff that does not infiltrate or become directed to a
recharge basin or pond).
The land within the primary drainage area is especially critical to the health of the lake. The
land is lower lying and therefore there is a shallow depth to groundwater (thus reducing
opportunities for subsurface infiltration of rainwater). Precipitation falling on these areas is
more likely to become surface water within the lake or wetlands of the bog, and may act as a
conveyance mechanism for pollutants, sediments and debris in its path.
The primary drainage area and sub-drainage areas were delineated using the digital elevation
model (and edited to include some man-made stormwater infrastructures) are illustrated in
Figure 4-3. Stormwater recharge basins and ponds are shown in Figure 4-4 along with special
treatment basins (where stormwater is detained before entering the lake or bog) and mapped
drainage structures.
Appendix A provides the results of a stormwater runoff/pollutant loading analysis for the
primary drainage area performed by NP&V utilizing a parcel based methodology which
12
See http://www.esri.com/news/arcuser/arcuser498/hydrology.html for more information.
Page 24
Lake Ronkonkoma
assigns pollutant load values based upon general land use categories. This methodology is
consistent with work performed by SCDHS for the Peconic Estuary Program (PEP) and the
North Shore Embayments Watershed Management Plan as an update to the Long Island Sound
Study (LISS).
Stormwater from the primary drainage area is the primary determining factor for lake water
quality as it is less likely to be effectively recharged. It is noted that limited portions of the
area have runoff directed to treatment basins (that detain stormwater runoff and allow for
biological filtration by wetlands plants before the water reaches the lake); however, the model
assumes limited filtration by stormwater best management practices for runoff within this area.
The pollutant load model results estimate the possible volume and types of pollutants resulting
from stormwater generated in the primary drainage area.
4.9
Stormwater Runoff Basin Descriptions
The Lake Ronkonkoma watershed includes a variety of existing stormwater detention facilities.
Figure 4-4 illustrates the locations of stormwater receiving and treatment areas in the study
area. This figure depicts six types of stormwater handling systems which are described as
follows:
1. Dry recharge basins which divert all stormwater they receive into recharge.
2. Wet recharge basins which divert some stormwater into recharge, but may not be able
to recharge all the stormwater they receive during large rainfall events and are subject
to longer periods of inundation and potentially to overflow.
3. Dry or wet recharge basins which can be either wet or dry depending on recent
weather.
4. Treatment basins are areas near the lake that receive stormwater runoff and hold it
before discharging it to the lake (or the bog). This delay in reaching the lake allows for
natural attenuation of nonpoint source pollutants and settling of sediment before
stormwater reaches the lake.
5. Ponds in the area mostly are connected to the lake through shallow groundwater, but
any pond can have some stormwater diverted to it. None of the ponds identified have
any evidence of direct discharge to the lake or bog.
6. The Great Bog operates as a large treatment system, detaining stormwater and allowing
for treatment/biological uptake. The 1986 Study noted that it is possible for large
rainfall events to cause a flush of water to move through the bog and into the lake
taking with it sediment runoff and decomposition products. Since the 1986 Study,
improvements to Smithtown Boulevard and Lake Shore Road limit the amount of water
that may move from the bog into the lake. The maximum amount of flow between the
bog and the lake has never been measured, but observations during the largest
Page 25
Lake Ronkonkoma
measured rainfall event since the road improvements (10/15/05) did not indicate any
water flowing over Smithtown Boulevard; however, Shore Road within the County
Park along the lake’s northern edge was almost completely submerged at that time.
Control of stormwater runoff using stormwater handling systems was a major recommendation
of the 1986 Study. Many recommendations have been implemented as discussed in Section
2.0 of this report. The completion of construction of a new retention basin proposed opposite
the Town of Brookhaven Beach (Lake Shore Road at the southern end of the lake) is the
largest single opportunity that is still pending related to stormwater improvements. This basin
would receive stormwater from a large drainage area where little storage is provided and would
provide significant improvements with regard to nonpoint source pollution to the lake.
Another key opportunity is the continued housekeeping and maintenance of existing recharge
and treatment basins. Preventing stormwater culverts from clogging by keeping up with street
sweeping and removal of yard waste is a key prevention measure for removing potential
pollutants before they reach the surface water of the lake. Sediment and solids removal from
catch basins and initial settling structures is also a critical maintenance practice. Keeping
recharge and treatment basins operating as designed is an important practice that goes a long
way towards improving and maintaining water quality in the lake.
4.10
Resident Canada Geese
Water quality of Lake Ronkonkoma has suffered impacts from the resident Canada Goose
population in the areas surrounding the lake. In addition, this factor affects the quality of life
for residents, since the Town beaches have been closed for bathing for three years due to
bacteriological inputs from goose waste. The following provides a summary of the problem
and potential solutions.
The increase in bacterial levels, primarily blamed on resident geese, has resulted in the closure
of the public beaches at Lake Ronkonkoma since 2003. Bacteriological testing is performed to
determine whether it is safe to swim from a human health perspective. The bacteria tested for
in water does not in itself cause human illness, however, the presence of certain bacteria
provides an indication of fecal contamination, which may in turn indicate the presence of
illness causing pathogens13. The County adopted new bacterial standards in June 2004 and
now tests for E. coli/Enterococci, instead of the formerly used fecal and total coliform tests.
Both are bacterial indicators which occur in the intestinal track of warm blooded animals. The
EPA has found better correlation between swimming-associated gastrointestinal illness and
Enterococci in fresh waters. Beach closures are considered when two successive results
exceed the single sample criteria of 61 colonies per 100 ml or when the log-average of all
13
It is noted that it is impractical to test for pathogens, since the tests are not as simple as testing for
bacteriological indicators. Also, there is an immeasurable number of pathogens and the presence of one pathogen
does not provide any indication of the presence of others, therefore it would be impossible to test for all
pathogens.
Page 26
Lake Ronkonkoma
samples collected in a 30 day period exceeds the multiple sample criteria of 33 colony forming
units (cfu)/100 milliliters (ml). The Town of Brookhaven Beach was never opened for
swimming between 2003 and 2007 due to the continual presence of geese and resultant high
bacteria at the waterfront. The Town of Islip Beach experienced a greater number of closure
days in 2005 than during its entire history (before that, the greatest number of closures was 21
days in 1996).
Local Initiatives
Based upon an interview with the president of the local chamber organization, NP&V learned
of several management strategies which have been attempted in recent years to control the
goose population with limited success. The Chamber has employed a firm to conduct hazing
using border collies. In addition, a beach raking program was implemented to remove the
goose droppings. The combination of hazing and the beach raking was noted to improve the
quality of the beach dramatically; however, there was no coordinated data from the SCDHS to
determine whether it would have resulted in improvements in water quality to allow beaches to
reopen.
Suffolk County and The Nature Conservancy have assembled volunteers to conduct an egg
oiling program at Lake Ronkonkoma in previous years under a federal depredation permit from
the U.S. Fish & Wildlife Service (USF&WS). However, egg oiling was not conducted in 2007
due to lack of coordinated efforts.
It is noted that volunteer programs are difficult to maintain over time without diligent
coordination, especially programs which require a high level of intricately timed involvement
on an annual basis. It is noted that the strategies that have been implemented by the
community represent a gallant effort to protect the resource while being sensitive to the
wildlife.
NP&V has received Geese Peace training and consulted other studies (Smith et al. 1999,
Shinn et al. 2001) regarding geese management. The consensus is that more than one strategy
is necessary for the stabilization of resident geese populations. It is imperative to understand
that resident Canada geese have a 20 year life cycle and instinctively return to their general
area of birth each year to mate and nest. Therefore, ultimate control of this population will
require a long term consistent program that involves integrated strategies. A successful
program requires an organization to take the lead on coordinating implementation each year.
For Lake Ronkonkoma, it is recommended that a grant-funded wildlife management plan,
which incorporates humane techniques (such as Geese Peace), be prepared for control of the
resident geese and implemented by a local organization to ensure that the management is
performed consistently and with measurable results. Geese Peace programs have been
successfully implemented throughout Nassau County which is in its third year of conducting
population stabilization techniques.
Given the established nest sites surrounding Lake Ronkonkoma and the nesting behavior of
resident geese, an egg oiling program appears to be critical for humane and successful long-
Page 27
Lake Ronkonkoma
term population stabilization. Additional strategies conducted throughout the year are
recommended to supplement the annual egg-oiling each spring to optimize the success of the
program. Based on the extent of the current nesting population, type of habitat surrounding
Lake Ronkonkoma, and residential land uses which surround the lake, the Geese Peace
population stabilization program is specifically recommended for Lake Ronkonkoma14. This
program entails the following integrated strategies:

Population Stabilization
Egg oiling by trained volunteers or staff helps control the resident geese population humanely.
Also, when there are no goslings the parents and rest of the flock have no need to stay at the
nesting site. Site registration with USF&WS is required.

Exclusion
Trained Border collies chash the geese away from areas that are unsuitable (e.g. beaches). The
geese learn that those areas are unsafe and they move to forage areas and ponds where they are
not a nuisance. NYSDEC Nuisance Wildlife Control Permit required.

Foraging Areas
Areas are provided where geese are tolerated and a small population of resident geese can be
sustained without creating a nuisance.

Landscaping
Plantings and tall grasses, strategically placed around the lake, will provide a perceived hiding
place for predators and will interrupt the connection between the lake and upland. This
reinforces the effectiveness of the use of Border collies.

No Feeding Policy
Feeding geese can be harmful to the
animals’ health and encourages
geese to stay and concentrate in
areas where they may become a
nuisance. Friendly reminder signs
can be posted in recreation areas
along Lake Ronkonkoma to educate
the public on why it is important to
NOT feed the ducks and geese.

Repellents
Nontoxic chemical repellents (which give geese a “stomach ache’) and discourage geese from
eating grass.

Integrated Strategies
A combination of egg oiling, Border collies, landscaping and chemical repellents will keep
geese away and create an environment unattractive to geese.
14
The Geese Peace method and egg-oiling protocol are endorsed by the American Human Society and People for
the Ethical Treatment of Animals (PETA).
Page 28
Lake Ronkonkoma
Prior to 2007, a federal Depredation Permit from the USF&WS was required to conduct
resident Canada geese population stabilization involving the addling of eggs (e.g. oiling,
shaking, or other disturbance). However, federal permits are no longer required in most states,
including New York, and the USF&WS now only requires registration of sites where goose
nests will be managed (Depredation Permits are still available in states where registration is not
allowed). This process was made even simpler in 2008, when the ability for individuals and
organized
groups
to
register
sites
on-line
became
available
(https://epermits.fws.gov/eRCGR/geSI.aspx). Municipalities are still able to obtain an areawide permit, and are also able to register on-line, as long as there is written documentation of
owner’s consent for privately owned lands within the nest management area. Common
properties can also be registered by Home Owner’s Associations or other community
associations.
USF&WS registration of nest management allows for the depredation of resident Canada
Geese nest and egg destruction. Adult birds must never be touched, goslings must never be
removed, and trespassing on private lands without owner’s consent is not allowed. The Geese
Peace method fits under the USF&WS registration requirements and protocol for egg oiling.
The only distinctions are that the Geese Peace method does not allow for destruction of nests
and it requires that eggs must be oiled within two weeks of incubation (prior to the formation
of an air sac), whereas the USF&WS protocol allows the egg to be addled anytime during
incubation.
In 2006, the federal government issued a final rule allowing for expanded hunting methods and
hunting seasons for resident Canada Geese under a state hunting license. With state
authorization, municipalities can perform a round-up of resident geese (which involves
capturing and destroying the birds). However, the hunting and round-up of resident geese in
urban areas is a short-sighted solution, whereas routine and methodical geese population
stabilization techniques are better accepted by the general public and provide a long-term
solution for making areas unattractive to resident geese.
A formal management plan should be prepared and implemented to reduce the number of
resident Canada geese in Lake Ronkonkoma and should include recommendations related to
funding the coordination and implementation of humane stabilization methods. The program
should be monitored and the success of the program documented with modifications to the plan
made if needed. The plan should provide for measurable goals including deadlines for
implementation of more stringent measures if more moderate strategies are not successful.
Control of the Resident Geese at Lake Ronkonkoma is critical to improving water quality and
ensuring that the residents may safely enjoy the Town Beaches in Brookhaven and Islip.
Page 29
Lake Ronkonkoma
4.11
Land Use
Figure 3-1 is used to compare the Recommended Land Use Map from the 1986 Study to the
present land use15. The two figures have different areas shown and utilize similar legend colors.
Several properties designated as open space in the 1986 figure are now owned by public entities
and are thus designated as open space in the updated figure.
Land use has changed, but not dramatically since much of the study area was already
developed in 1986. In comparing census information, the 2000 population within the Lake
Ronkonkoma drainage area was 13,927 persons which is 100 more than in 1990 or a 0.7%
increase. This increase is not as significant as the countywide increase that occurred during
this period of 1.2%. The limited change in land use in association with the small population
increase seems to illustrate that the period of heavy development for the area has passed. Very
little vacant buildable land exists in the study area which is not owned by public agencies.
Census data indicates that very little population change has occurred between 1990 and 2000,
while significant changes occurred during the time frames of 1980-1990 and 1970-1980.
The concept of a recreational trail surrounding the lake has been raised during meetings with the
task force. Land use and ownership of lands adjacent to the lake is a clear inquiry necessary to
determine the feasibility of such a project. Figure 3-4 has been provided to illustrate the public
(in some cases presumed) and private properties located adjacent to the lake. The lake provides a
recreational resource which merits public access, which can be limited by private ownership.
The ownership figure indicates that the areas of private ownership directly adjacent to the lake
are actually fairly limited, which provides a potential opportunity for a lakeside walk that loops
the entire lake. It is expected that the walk would be a combination of trail, boardwalk and in
some areas road “detours”.
The Bavarian Inn, which is closed due to the flooding as a result of the lake level was recently
approved for acquisition by Suffolk County. The reutilization of this parcel should consider
planning for a future lake loop trail as discussed above.
4.12
Zoning
The 1986 Study made several recommendations with respect to zoning, primarily to reduce the
potential for increased density of residential use.
Although zoning classifications in the three towns and one village differ, the legend in Figure 32 reflects the common zoning areas grouped by general use and lot size (low and medium
density) as was prepared for the 1986 Study. A comparison of the proposed zoning map from
the 1986 Study and Figure 3-2 reveals that a number of changes were made in accordance with
15
Land use is identified by the 3-digit NYS Real Property Assessment code and labeled using the same colors used by Suffolk
County Department of Land Planning in the 1986 Study. Land use data was provided in 2005 which contained some outdated
information; the land use field was updated based upon field observations as feasible.
Page 30
Lake Ronkonkoma
the recommendations.
In Smithtown Township, the recommendation included “up zoning” of vacant parcels zoned for
high density residential use in a high water table area. In one case, a parcel recommended for
upzoning has since been developed with multi-family housing. Other recommendations
involved proposed rezoning of commercial use properties to medium density residential; in
addition, the 1986 Study recommended upzoning of undeveloped areas that were experiencing
flooding. In this case, the Town of Smithtown chose to rezone those properties to CF
(Community Facility), whose permitted uses include single family homes which require a
minimum parcel size of 5 acres. It is noted that one 5 acre private property adjacent to the Great
Bog in this zoning district was acquired by Suffolk County in 2006.
In Islip Township, zoning amendments resulted in replacing commercial land adjacent to the lake
to AA (medium density residential zoning), consistent with the surrounding parcels.
In the Town of Brookhaven, zone changes were implemented consistent with the
recommendations of the 1986 Study. The lands adjacent to the lake are no longer commercially
zoned. A portion of the residential land was up zoned to require a minimum lot size of 22,500
SF (considered low density for the purpose of this study). In some cases, where the 1986 Study
recommended up zoning to medium density, the Town of Brookhaven exceeded the
recommendation by zoning to a low density residential zone.
Page 31
Lake Ronkonkoma
5.0
RELEVANT PROGRAMS AND STUDIES
Chapter 3 of the 1986 Study included a description of past and present governmental activities
and programs affecting the lake and the surrounding community.
SCDHS engaged in several monitoring programs at the time of the original study which are
described as follows:
1. Groundwater Monitoring Wells: Using 10 existing wells (four upgradient and six down gradient)
plus five additional upgradient wells installed for the study, the SCDHS monitored groundwater
elevation and flow direction, nitrate-nitrogen levels, and organic chemicals. The six down
gradient wells indicated high levels of nitrate-nitrogen levels, an indication of high density
residential development, whereas the upgradient wells only occasionally exhibited high nitratenitrogen levels.
2. Private Wells: A survey of private drinking water wells in the vicinity (north of the lake),
indicated nitrate-nitrogen concentrations above the drinking water standard in one of twelve
wells.
3. SCDHS Bathing Beaches: Bathing beach samples were collected for over 200 beaches for total
fecal coliform. In 1985, the two beaches were sampled ±20 times with no closures required under
the NYS Sanitary code requirements at that time, although there were individual samples with
elevated bacterial counts.
4. Sewage Disposal Systems: In August 1984, a sampling of twelve sanitary systems immediately
north of the lake was conducted. One of twelve had a failing sanitary system due to flooding. In
addition, a dye test was conducted for the apartments on the north side of the lake with no
indication that any malfunction was occurring at that time.
5. A survey of all restaurants and temporary residences on Lake Ronkonkoma was conducted in
August 1985 with dye testing of the sewage disposal systems. No malfunctioning systems were
found.
The monitoring of the lake swimming areas is part of an ongoing program by the SCDHS. The
monitoring of groundwater wells by the SCDHS has virtually ceased. Other programs involving
sanitary system investigations were conducted specifically for the 1986 Study; however, SCDHS
does respond to complaints or specific incidents when brought to their attention.
5.1
Programs
A reexamination of past and present governmental activities and programs affecting the lake
and the surrounding community has been completed. The status of recommendations from the
1986 Study are evaluated below (i.e. acquisitions, drainage improvements and maintenance
Page 32
Lake Ronkonkoma
programs) and are discussed in this section to determine whether the previous
recommendations remain valid.
The following recommendations from the 1986 Study have been achieved:
1. Vacant properties that might be used for stormwater control have been purchased.
2. The former trailer park adjacent to County parkland has been acquired and the majority of the
trailer units have been removed.
3. Prohibition of new stormwater runoff has been accomplished through the regular upkeep and
redesign of the preexisting basins. The only development to take place within the drainage area
is properties in the far northwest part of the drainage area in the triangle between CR 16 (Lake
Shore Road), Gibbs Pond Road and Old Nichols Road (however, the majority of this
development is outside of the drainage area).
4. New drainage systems were installed and designed.
5. Public outreach efforts by the SCWA have been increased which urge citizens to use organic
fertilizer which is less likely to have an impact on the environment.
6. Public outreach efforts regarding stormwater impacts are ongoing by Townships surrounding
the lake and Suffolk County.
7. The Bavarian Inn has been approved for acquisition by the County.
Unfortunately, none of the research related recommendations have been implemented. The
1986 Study states that the USGS will be gauging stream flow from the bog into the lake.
However, no measurements of this kind exist on the USGS NWIS website
(nwis.waterdata.usgs.gov/usa/nwis) nor do any of the representatives contacted have any
knowledge of such a gauge. It would be beneficial to resume a water quality sampling
program such as is shown in the 1986 Study on Figure 4-1. Sampling and analysis into the
eutrophic status of the lake16 is a recommendation that should be implemented in the future. It
is noted that it may now be possible to collect periodic Chlorophyll A measurements for the
lake using remote sensing data available from NOAA, JPL (http://poet.jpl.nasa.gov) or other
sources without new field work.
Predicted and measured values of phosphorous in the 1986 Study were not in agreement. This
raises the question of whether or not there is some additional unknown source of phosphorous
being added to the system, or whether the model does not represent phosphorous inputs well.
Running the model taking into account further changes in land use, development, and citizen’s
use of phosphorous-containing detergents should be performed so that the results may be
analyzed to answer the above referenced question.
16
1986 Study, Appendix F
Page 33
Lake Ronkonkoma
5.2
Preparation of a TMDL
Lake Ronkonkoma is a targeted priority waterbody listed on the DEC 303(d) List of Impaired
Waterbodies17. The New York State Section 303(d) List of Impaired/TMDL Waters identifies
those waters that do not support appropriate uses and that may require development of a Total
Maximum Daily Load (TMDL) or other restoration strategy to attain quality standards. The
2006 NYS Section 303(d) List was submitted to USEPA September 2006 and approved by the
USEPA Region 2 on July 5, 2007. At this time, development of the 2008 Section 303(d) List
is in progress; until the Final 2008 list is approved by the EPA, the 2006 Section 303(d) List is
considered to be the most current List of Impaired/TMDL Waters.
The analysis that supports the 303(d) List is provided in a DEC report entitled the Waterbody
Inventory/Priority Waterbodies List (PWL) Report. The most recent DEC Waterbody
Inventory/Priority Waterbodies List Report for the Long Island region was published in April
of 2002 and includes inventory and assessments for each waterbody in the area.
A March 2001 waterbody assessment prepared for Lake Ronkonkoma included algal/weed
growth, nutrients and pathogens as the pollutants impacting lake water quality and listed public
bathing, aquatic life and recreation as uses that were impacted by pollution (see Appendix B2). Sources of pollutants are noted as urban runoff (known) and storm sewers (suspected).
The DEC updated some of the waterbody assessments, including the one prepared for Lake
Ronkonkoma [updated in February of 2006 (Appendix B-3)]. The updated assessment for
Lake Ronkonkoma includes the same pollutants as identified in 2001 (although specifying
phosphorus as the nutrient of concern). Urban/storm runoff are reported as a known source of
pollution and suspected source of pollutants are reported as “other sanitary discharge” in
comparison to “storm sewers” on the 2001 assessment. Based on a personal communication
with staff of the NYSDEC Division of Water – Water Assessment and Management, there was
a decision to remove the term “storm sewers” from the potential source of pollutants.
According to the NYSDEC Division of Water, the change was probably an administrative
change since the NYSDEC no longer uses the “storm sewers” category. It was surmised by
NYSDEC personnel that the category “other sanitary discharge” was used as a replacement
term and noted it as a suspected source of pollutants. This may be revised to read “Urban
Runoff” when the assessment is updated.
Lake Ronkonkoma was included on the original 303(d) list citing each of the pollutants in the
waterbody inventory assessment. However, the Final 2004 list (and the subsequent final 2006
list) “delisted” Lake Ronkonkoma for algal growth/weeds, as these are not pollutant, but rather
a possible result of nutrient influx18. Lake Ronkonkoma is also currently included on the draft
2008 list.
17
Section 303(d) refers to Section 303(d) of the Federal Clean Water Act which requires states to periodically assess and
report on the quality of waters in their state.
18
It is noted that Lake Ronkonkoma had been the subject of USEPA review regarding the 2002 Section 303(d) List; comment
was made on the designation of Lake Ronkonkoma impairments from algal/weeds growth as being a result of general pollution
rather than a specific pollutant that can be allocated through a TMDL. USEPA did not object to the lake’s designation on the
303(d) list for other pollutants, but asked for additional information and clarification. Recreational uses in Lake Ronkonkoma
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Lake Ronkonkoma
The following is an excerpt from the introduction of The Final New York State 2006 Section
303(d) List of Impaired Waters Requiring a TMDL/Other Strategy (NYS DEC, May 17,
2007):
The Federal Clean Water Act requires states to periodically assess and report on the quality of
waters in their state. Section 303(d) of the Act also requires states to identify Impaired Waters,
where specific designated uses are not fully supported. For these Impaired Waters, states must
consider the development of a Total Maximum Daily Load (TMDL) or other strategy to reduce
the input of the specific pollutant(s) that restrict waterbody uses, in order to restore and protect
such uses. An outline of the process used to monitor and assess the quality of New York State
waters is contained in the New York State Consolidated Assessment and Listing Methodology
(CALM). The CALM describes the water quality assessment and Section 303(d) listing process
in order to improve the consistency of assessment and listing decisions.
The waterbody listings in the Section 303(d) List are segmented into a number of categories.
The various categories, or Parts, of the list are outlined below.
FINAL 2006 Section 303(d) List of Impaired Waters Requiring a TMDL
Part 1 Individual Waterbody Segments with Impairments Requiring TMDL Development
These are waters with verified impairments that are expected to be addressed by a
segment/pollutant-specific TMDL or other restoration strategy.
Part 2 Multiple Segment/Categorical Waterbody Impairments Requiring TMDL Development
These are groups of waters affected by similar causes/sources where a single TMDL may be
able to address multiple waters with the same issue. Part 2 is subdivided into:
• Waters Impaired by Atmospheric Deposition (acid rain)
• Waters Impaired by Fish Consumption Advisories
• Waters Impaired by Shellfishing Restrictions
Part 3 Waterbody Segments for which TMDL Development May Be Deferred
These are waters where scheduling of TMDL development may be deferred pending
verification of the suspected impairment, the cause/pollutant related to the impairment, or the
effectiveness of other restoration measures in place. Part 3 is subdivided into:
a) Waterbody Segments Requiring Verification of Impairment
b) Waterbody Segments Requiring Verification of Cause/Pollutants
c) Waterbody Segments Being Address Through Other Restoration Measures
Impaired/Delisted Waters Not Included on the 2006 Section 303(d) List
Included with but separate from the 2006 Section 303(d) List is a supplemental listing of Other
Impaired Waterbody Segments Not Listed (on 303(d) List) Because Development of a TMDL is
Not Necessary. The purpose of this supplement is to provide a more comprehensive inventory of
waters of the state that do not fully support designated uses and that are considered to be
impaired. Section 303(d) of the Clean Water Act stipulates that impaired waters that do not
are restricted by excessive algal/weed growth. The EPA determined that since algae/weeds cannot be directly addressed by a
TMDL (this impairment is an example of pollution, rather than pollutant). Thus, Lake Ronkonkoma was delisted for this
category.
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Lake Ronkonkoma
require a TMDL are not to be included on the Section 303(d) List. There are three (3)
justifications for not listing an impaired water:
Category 4a – TMDL development is not necessary because a TMDL has already been
established for the segment/pollutant.
Category 4b – TMDL is not necessary because other required control measures are expected to
result in restoration in a reasonable period of time.
Category 4c – TMDL is not appropriate because the impairment is the result of pollution,
rather than a pollutant that can be allocated through a TMDL.
Delisted Waters
A separate list of waters that were included on the previous (2004) Section 303(d) List, but that
are NOT included on the 2006 List is also presented. This information provides some linkage
and continuity between the previous and proposed new list. The specific reason that the
waterbody no longer appears on the List (i.e., delisting action, re-assessment, re-segmentation,
etc.) is also presented. Some of these waters (those that remain Impaired) also appear on the
list of Other Impaired Waterbody Segments Not Listed Because Development of a TMDL is Not
Necessary.
Lake Ronkonkoma is included in Part One of the Final 2006 303(d) List (Individual
Waterbody Segments with Impairments Requiring TMDL Development) which implies a high
priority for preparation of a TMDL.
The PWL assessments for Lake Ronkonkoma for 2001 and 2006 are provided in Appendices
B-2 and B-3 respectively.
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Lake Ronkonkoma
6.0
6.1
WATER QUALITY
Source Water Assessment Program
The 2003 Source Water Assessment Program (SWAP, 2003) prepared by CDM (Camp,
Dresser and McKee) determined groundwater capture zones for public water supply
withdrawal wells in Suffolk County. The capture zones represent areas on the ground’s
surface where infiltrating precipitation enters the groundwater system and will eventually enter
the screened zone of that particular drinking water well. A 2-year capture zone (cz) is an area
where some of the infiltrating precipitation will be captured by the pumping well within two
years. There are some important assumptions involved in defining capture zones.
1. For the Long Island simulation, the groundwater system is steady-state (i.e. the water table and
deeper aquifer water levels are constant and have reached equilibrium between inflow from
recharge and discharge through pumping and stream flow and subsurface discharge).
2. The pumping rates for all the pumping wells are a constant value (never varying), and all the
wells are always operating at that constant rate (the same assumption is used for stream flow).
3. The assumed geologic coefficients for ground water flow are accurate (porosity and hydraulic
conductivity of aquifers and confining layers).
4. The equations of groundwater flow can be approximated with only small errors.
The last of these assumptions is the most valid. There are few SWAP capture zones and
SCWA wells that lie within the watershed area of Lake Ronkonkoma. Only the 50, 75 and
100-year capture zones for well S-77010, (a well in Lakeland, Town of Islip located to the
southwest of the lake, at a distance of approximately 2.2 miles) touches the lake and its
northern marsh.
6.2
Water Quality
In preparation for the analysis that took place for the 1986 Study, the following water quality
investigations were performed:
1. An extensive lake water quality sampling program which involved the measurement of the
chemical, physical and biological characteristics of the lake under dry weather conditions was
conducted. The biological characteristics measured included the bacteria, phytoplankton and
zooplankton.
2. A wet weather study was performed to determine the relative impact of rainfall and runoff on
the lake water quality. Fecal and total coliform bacteria along with numerous chemical
parameters were analyzed for this study.
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Lake Ronkonkoma
3. Stormwater runoff sampling was conducted to assess the quality of the stormwater runoff
entering the lake. Stormwater runoff samples were analyzed for bacteriological and chemical
parameters.
4. A groundwater quality survey involved the installation and sampling of wells upgradient of the
lake in order to evaluate the quality of the groundwater in that portion of the Upper Glacial
aquifer that supplies groundwater to the lake.
All of the programs listed above ceased following the completion of the 1986 Study. The data
that is currently collected is scarce and does not provide the basis for a full water quality
assessment of current conditions or for a comparison or trends analysis. This study does
provide an assemblage of available water quality data collected since 1986, including the
SCDHS bathing beach data. While the data is limited, observations may be made with respect
to the limited data that exists, and changes that have occurred since 1986. In addition,
recommendations are provided regarding the type of water quality monitoring that is
appropriate for the future monitoring of Lake Ronkonkoma.
6.3
Current Water Quality Monitoring
This section provides a summary and update of past and current of sampling results for surface
water quality, stormwater pollution loading estimates, groundwater quality, and waterfowl
activity from available existing information. Summary sheets for each data set have been
compiled which identify the source of data, parameters analyzed, purpose of sampling and
comments regarding the data. Summary Sheets are provided in Appendix C-1 and data sets
are provided in Appendix C-2. Figure 6-1 is provided to illustrate the locations of water
quality data samples (where known). Section 6.4 provides a description, source and summary
of the data.
6.4
Surface Water Quality Data
6.4.1
Cyanotoxin Monitoring
Cyanobacteria are a common family of blue green algae which are typically associated with
over-enriched eutrophic and poorly flushed waters. There are several potentially toxic subspecies of these algae capable of producing harmful cyanotoxins, such as hepatoxins (e.g.
microcystin) which target the liver. The abundance of these toxins in aquatic ecosystems has
serious implications for wildlife and human health, as multitudes of sicknesses and even deaths
have been associated with the consumption of contaminated water. Nutrient loading combined
with warm temperatures is known to increase algal blooms in summer months, and is therefore
also thought to increase the potential growth of harmful varieties of cyanobacteria in poorly
flushed waters.
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Lake Ronkonkoma
The following provides a summary of water quality studies performed by Christopher J.
Gobler, PhD as included in the July 2007 report entitled “Monitoring of toxic cyanobacteria in
Suffolk County Lakes. Final report to the Suffolk County Department of Health Services,
Office of Ecology.”
A four year study of 20 lakes throughout Suffolk County was undertaken by Professor
Christopher Gobler, PhD, to assess the presence of toxic cyanobacteria blooms in recreational
areas and the factors which are associated with promoting these blooms. While the majority of
the lakes studies had levels below the threshold considered to be a low recreational risk by the
World Health Organization (WHO), Lake Ronkonkoma was identified as a lake which posed
moderate-to-high risks to human health for recreation at various times during the study. The
guidelines established for municipalities by the WHO for microcystin concentrations in natural
water bodies are 1 µL-1 for drinking water supplies, 2 to 4 µL-1 for low recreational risk, and 20
µL-1 for moderate recreational risk. Water quality samples obtained from 2004 through 2005
in Lake Ronkonkoma revealed an average annual mycrocystin concentration of 15.0 ±10.75
µL-1, with a maximum concentration of 78.8 ±18.0 µL-1 on June 8th, 2005. High risk
concentrations are indicated to be in a cyanobacterial algal mat which can form near the shore,
and are to be avoided. Islip Town Beach was the primary sampling station; however, cross
lake transects were conducted and determined that the blooms observed at the Islip Beach were
lake-wide events.
Among other sampled water quality parameters over the course of the study, Lake
Ronkonkoma exhibited levels of chlorophyll and nutrients (nitrogen and phosphorus) that
deem it a eutrophic system by EPA guidelines.
As toxic blue green algae blooms are associated with stagnant, eutrophic waters, the following
two approaches should be tested as methods for reducing the occurrence and risk of toxic
cyanobacteria blooms in afflicted lake systems:
1. Install water circulators to push surface dwelling cyanobacteria to the bottom of the lake,
potentially preventing bloom occurrence; and
2. Target the reduction of primary sources of nutrients into Lake Ronkonkoma in conjunction
with monitoring to assess the relation of nutrient loads on algal blooms.
The continued monitoring of Lake Ronkonkoma for cyanotoxin levels and associated
ecological-based studies (e.g. chemical, physical and biological factors) is strongly warranted
to further elucidate the factors which promote the presence of these toxins. Continued water
quality monitoring will also serve to track the success of implemented nutrient reduction
strategies. An adaptive management approach for Lake Ronkonkoma should be utilized as the
understanding of cyanotoxins is improved and in order to enhance water quality while
minimizing health risks to humans and animals.
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Lake Ronkonkoma
6.4.2
SCDHS Bathing Beach Monitoring
The Suffolk County bathing beach monitoring program has issued yearly reports of their water
quality monitoring results, for indicators of pollution dangerous to bathers. The County
documents include sample results and beach closings. Lake Ronkonkoma has had poor water
quality at its two bathing beach sampling sites during the warm summer months (which are
when sampling takes place) resulting in considerable beach closings. While the parameters
monitored have changed and the regulations have become stricter for beach closings, it is
expected that the beaches would have been closed a significant amount of time under any rules
because of bacteria detected along the lake shore.
Prior to June 2004, fecal coliform was used as the bacteriological indicator. According to
NYSDEC guidelines, bathing beaches were safe to remain open if the mean total coliform
bacteria was less than 70 ‘Most Probable Number’ (MPN)/100 ml and 10% or less of measured
stations are under 330 MPN/100 ml. The guidelines for fecal coliform were for the mean of
the samples to be less than 14 MPN/100 ml and 10% or less of measured stations under 49
MPN/100 ml (Note: NYSDEC guidelines use mean values of samples; note that median values
are shown in the table). The County adopted new bacterial standards in June 2004 and now
tests for E. coli/Enterococci, instead of the formerly used fecal and total coliform. Both are
bacterial indicators which occur in the intestinal track of warm blooded animals. The EPA has
found better correlation between swimming associated gastrointestinal illness and Enterococci
in fresh waters. Beach closures are considered when two successive results exceed the single
sample criteria of 61 CFU per 100 ml or when the log-average of all samples collected in a 30
day period exceeds the multiple sample criteria of 33 CFU/100 ml. The Town of Brookhaven
Beach was not opened between 2003 and 2006 for swimming due to the continual presence of
geese at the waterfront. The Town of Islip Beach experienced a greater number of closure
days in 2005 than during its entire history (before that, the greatest number of closures was 21
days in 1996).
The water quality data summarized in Table 6-1 include the three bacterial indicators sampled
at two beach sites on Lake Ronkonkoma during the summer months. Values are summarized
in the Table 6-1. Table 6-2 indicates the beach closure days at Lake Ronkonkoma in recent
years; these data are also illustrated in the following histogram.
TABLE 6-1
BATHING BEACH DATA SUMMARY
Sample – name location
Brookhaven Fecal Coliform
Islip Fecal Coliform
Brookhaven Total Coliform
Islip Total Coliform
Brookhaven Enterococci
Islip Enterococci
years
8
8
7
8
3
3
units
MPN/100 ml
MPN/100 ml
MPN/100 ml
MPN/100 ml
CFU/100 ml
CFU/100 ml
median
285
80
500
230
72
32
min
1
1
20
1
1
1
max
16000
16000
16000
5000
2175
1088
count
112
153
112
152
59
103
MPN/100 ml – most probable number per 100 milliliters
CFU/100 ml – colony forming units per 100 milliliters
Page 40
Lake Ronkonkoma
TABLE 6-2
NUMBER OF BEACH CLOSURE DAYS
Year
1988
1989
1990
1991
1992
1996
1997
1998
Brookhaven
23
27
2
21
0
67
0
11
Islip
23
12
5
21
3
21
13
12
Year
2000
2001
2002
2003
2004
2005
2006
2007
Brookhaven
27
25
104
All
All
All
All
All
Islip
0
0
3
0
5
40
14
9
CHART 6-1
Summary of Lake Ronkonkoma Bathing Beach Closures
1988 - 2007
200
All
All
All
All
160
All
180
140
104
120
100
67
80
5
0
3
0
9
14
25
27
11
12
0
0
13
21
0
3
21
21
27
2
5
0
12
20
23
23
40
40
60
1988 1989 1990 1991 1992 1996 1997 1998 2000 2001 2002 2003 2004 2005 2006 2007
Brookhaven
Islip
A full set of bathing beach data for Lake Ronkonkoma for the years 1988 to 2007 is provided
in Appendix C-2.
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Lake Ronkonkoma
6.4.3
USGS Monitoring
The USGS has sampled water quality in Lake Ronkonkoma and those values are available on
the agency’s website. USGS sampling locations are at the northwest part of the lake
corresponding to the Smithtown Beach and shown in Figure 6-1. For 01306405, there are
three samples available since the year 2000 (all in August, 2002).19 The samples were taken at
the “Smithtown Beach” (which is the Suffolk County Park) on the north side of the lake.
These water quality data are from the USGS NWIS system which is available on the internet
(http://nwis.waterdata.usgs.gov/ny/nwis/qw). A sample of the parameters measured and the
dates for samples are provided in Table 6-3.
TABLE 6-3
SAMPLE OF USGS WATER QUALITY DATA PARAMETERS
Date of
sample
5/6/1966
4/22/1971
7/6/1973
9/20/1973
1/3/1974
4/3/1974
6/18/1974
9/8/1974
1/2/1975
3/24/1975
6/25/1975
10/1/1975
12/30/1975
3/24/1976
6/24/1976
9/24/1976
8/16/2002
8/16/2002
8/19/2002
Dissolved
oxygen, water,
unfiltered,
milligrams per
liter
11.8
8.4
1.7
7.1
6.3
2.4
4.9
12.2
10.4
8.4
2.7
2.7
3.8
pH, water,
unfiltered,
field,
standard
units
5.8
6.6
7.1
5.1
7.3
6.4
6
5.7
6.7
6.2
6
6.4
5.5
6.9
6.7
7.1
6.3
6.3
6.4
Organic
nitrogen, water,
unfiltered,
milligrams per
liter
Total nitrogen,
water,
unfiltered,
milligrams per
liter
0.43
0.4
0.21
0.57
0.09
0
0.15
0.4
0.46
0.34
0.4
0.92
0.78
1
1.5
0.92
1.3
1.8
1.1
0.84
1.4
2.2
0.62
0.95
1.1
Chloride,
water,
filtered,
milligrams
per liter
13
13
13
18
17
18
22
20
16
19
19
18
24
16
17
18
Water quality data indicate variability for all parameters. August and warmer month DO levels
are decreased relating to less mixing and/or algal bloom die-offs. pH is within an expected
19
For USGS 01306415, there is only one sample from 1973, taken at a location near the Brookhaven Beach.
Page 42
Lake Ronkonkoma
ranges and slighting acid. Nitrogen concentrations illustrate elevated concentrations from
sources within the watershed, and chloride concentrations are relatively low.
6.4.4
NYSDEC Monitoring
NYSDEC Fisheries collects data on a bi-annual basis and monitors temperature, dissolved
oxygen, and Chlorophyll A at a single station, near the State fishing access located near the
northwestern shoreline of the lake20. The most recent data is provided in Appendix C-2.
As per the NYSDEC Website, the purpose of the DEC Rotating Integrated Basin Studies
(RIBS) program is:
“… to assess water quality of all waters of the state, including the documentation of good
quality waters and the identification of water quality problems; identify long-term water quality
trends; characterize naturally occurring or background conditions; and establish baseline
conditions for use in measuring the effectiveness of site-specific restoration and protection
activities.”
The water quality data and information are used to support assessment and management
functions within NYSDEC Division of Water, including the Section 303(d) List of Impaired
Waters of the State. The 1999 sampling at Lake Ronkonkoma was part of a Long Island
Sound/Atlantic Ocean basin sampling of about a dozen lakes as part of the annual RIBS
monitoring program. This involved sampling of each project lake three times by Region 1
fisheries staff. A formal report was not generated as part of project. RIBS data is provided in
Appendix C-2.
The number of sampling points is too limited to provide any generalized surface water quality
information regarding DO nor is it known where the sampling occurred in the lake. If
sampling occurred solely in the deep hole area of the lake, the level of DO does not necessarily
reflect that of the rest of the lake. An observation based on the limited amount of data is that a
past problem has occurred with dangerously low and nearly depleted levels of DO in the lower
strata of the lake.
A sampling program with locations throughout the lake and DO measured at various depths to
bottom correlated to nutrients and other indicators would be extremely useful in determining
the extent of hypoxia and anoxic conditions.
20
The NYSDEC fisheries most recent annual report (2004/2005) lists fish surveyed in the summer of 2004 in Lake
Ronkonkoma as white perch, yellow perch, black crappie, bluegill, pumpkinseed, golden shiner, carp, banded killifish and
walleye (walleye in abundant population). The Fisheries Department has measured (but not published) some limnological
parameters of lake water quality including phosphorus, nitrogen, chlorophyll-A, and zooplankton. The NYSDEC reports a
successful summer stocking of young walleye and good catch during the summer sampling. The NYSDEC does not rate the
overall ambient lake water quality. Fishing information is available at http://www.dec.ny.gov/outdoor/7977.html.
Page 43
Lake Ronkonkoma
6.5
Groundwater Quality Data
6.5.1
SCDHS Observation Wells
The 1986 Study included six observation wells near the lake where water levels and water
quality samples were taken in 1984. Five of these wells were installed for the original study.
Although the water levels of the wells were observed and reported with respect to each other.
The measurements were with respect to an “assumed” datum. In other words, their measuring
point of top elevation of the well casing was not surveyed and thus the water level with respect
to mean sea level is not available. One of these wells (S-47718) is an existing well and
information is available on the USGS website through a database search at
http://nwis.waterdata.usgs.gov/ny/nwis/nwis; however, the remaining wells included in the
report were used solely for the 1986 Study and have since been abandoned.
6.5.2
USGS Observation Wells
A current search of wells in the area, for which data is available from the USGS website, yields
21 wells with some water quality or water level data (a similar number of wells with only
depth and aquifer data are available in the area). Of these wells, only five have current data
(water levels or water quality measured 2000 or more recent). A summary of these current
wells are summarized in Table 6-4.
TABLE 6-4
USGS GROUNDWATER DATA SUMMARY
Well name
S-1811
S-33380
S-37847
S-33379
S-72300
Notes
Water Level
only
Both water
level and
quality
Water
quality only
Both water
level and
quality
Water
quality only
Number of
water level
samples
Dates of
Observations
Number of
water quality
data samples
88
1987-2005
826
1968-2006
4
19681991
Magothy
0
-
20
19922004
Upper glacial
819
1968-2006
4
19681986
Lloyd
0
-
1
2005
unknown
Time
Period
Aquifer
Upper glacial
Wells S-37847 and S-33379 and S-33380 are located at the site of a SCWA well field. It is
noted that water levels near pumping wells can have great variation in their values depending
on the operation of the nearby pumping well and are not usually indicative of the regional
Page 44
Lake Ronkonkoma
groundwater elevation. Well S-72300 is quite far from the lake (±4,900 feet from the lake,
near the Sachem North High School) and well S-37847 is also not near the lake (±4,600 feet
from the lake, at the SCWA well field site); however, this well provides the greatest amount of
groundwater quality information in the vicinity of the lake. One additional consideration is the
fact that the groundwater at a drinking water pump station site is presumed to be of high
quality, and thus this cannot be considered an unbiased dataset if one is describing general
groundwater quality in the vicinity of the lake. Details regarding these data are included on
Water Quality Data Summary Sheets (#8 and #9) included in Appendix C-1.
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Lake Ronkonkoma
7.0
RECOMMENDATIONS
The following provides both general and specific recommendations regarding overall
management of the lake system.
General
1. Preparation of a Watershed Management Plan for Lake Ronkonkoma and its
surrounding area and adoption by the three townships. General recommendations
include control of intensification of land use, stormwater management improvement
projects, public outreach, water quality monitoring and watershed modeling to better
understand the hydrology and water quality of the lake and bog.
2. Preparation of a Bacteria and Pathogen TMDL for Lake Ronkonkoma. Lake Ronkonkoma is
included in Part One of the Final 2006 303(d) List (Individual Waterbody Segments with
Impairments Requiring TMDL Development) which implies a high priority for preparation of a
pollutant-specific TMDL or other restoration strategy. The development of a TMDL would
quantify the current pollutant loads to the lake, identify water quality targets and indicate by
how much current pollutant loadings would need to be reduced to attain water quality targets.
Once the TMDL is approved by the U.S. EPA, the Watershed Management Plan could then
include implementation strategies to meet the TMDL target goals.
3. Create a data repository for water quality data, research and mapping resources specific
to the lake system study area.
Land Use and Zoning
4. Support public acquisition of properties adjacent to the lake, with specific attention to
those adjacent to the Bavarian Inn, which was recently approved for acquisition by
Suffolk County.
5. Discourage increases in land use densities in the contributing areas of the lake and bog
unless site is connected to public water and sewage treatment with all stormwater
generated on the site adequately managed using best management practices on the
property.
Enhance Monitoring Program
6. The continued monitoring of Lake Ronkonkoma for cyanotoxin levels and associated
ecological-based studies (e.g. chemical, physical and biological factors) is strongly
warranted to further elucidate the factors which promote the presence of these toxins.
Continued water quality monitoring will also serve to enhance existing baseline water
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Lake Ronkonkoma
quality data and to track the success of implemented bacteria and nutrient reduction
strategies. An adaptive management approach for Lake Ronkonkoma should be
utilized as we expand our understanding of cyanotoxins and strive to improve water
quality while minimizing health risks to humans and animals. Consider building upon
the water quality database initiated by SUNY Stony Brook professor Christopher
Gobler to monitor cyanotoxin levels or working directly with Dr. Gobler to continue
water quality monitoring efforts.
7. As toxic blue green algae blooms are associated with stagnant, eutrophic waters, the
following two approaches should be tested as methods for reducing the occurrence and
risk of toxic cyanobacteria blooms:
a. Install water circulators to push surface dwelling cyanobacteria to the bottom of
the lake, potentially preventing bloom occurrence; and
b. Target the reduction of primary sources of nutrients into Lake Ronkonkoma in
conjunction with water quality monitoring to assess the relation of nutrient
loads to algal blooms.
8. Encourage funding for the establishment of water quality and quantity monitoring.
Water quantity measurements of water entering and leaving the treatment basins, the
Great Bog (from Smithtown pumping), and into Lake Ronkonkoma from the Great Bog
are appropriate. Measurement of lake elevation and nearby shallow and deep
groundwater potentiometry would be useful in understanding the recharge-discharge
relationship of ground and surface water. Water quality measurements should include
organic and inorganic nutrients and continual bacteriological sampling in treatment
basins, the bog, the lake, and nearby shallow groundwater.
9. Install a water level data logger at Lake Ronkonkoma to monitor the lake level.
10. Establish a citizen monitoring program similar to the Cornell Cooperative Program in
order to involve and educate stakeholders and gain useful data and information with
local insight.
Reduce Pollutant Load to the Lake System
11. Limit phosphorus loading by residents through public outreach. Scott’s fertilizer has
agreed to create a product with little to no phosphorus (the Chesapeake Bay program is
driving this initiative).
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Lake Ronkonkoma
12. Increase the program to control the Resident Canada Goose population. Prepare and
implement a formal Management Plan for control of the Resident Canada Goose
population consistent with the new USF&W Geese Peace program.
13. Continue with the objective for eliminating untreated stormwater runoff to the lake and
wetlands.
14. Implement the Lake Shore Road Drainage Improvement Project.
15. Continue maintenance of infrastructure (roads, stormwater pipes, recharge and
treatment basins) and routine clean out of catch basins and storm basins.
16. Provide yearly budget for upkeep of County and Town stormwater detention and
treatment basins. These structures need to be monitored and have periodic sediment
removal.
17. Encourage homeowners and business community to conduct routine sanitary system
maintenance, particularly those within the primary watershed area.
Public Outreach and Education
18. Prepare a mailing to all residents within the primary watershed area to inform them that
the water quality of the lake can be directly impacted by actions on their property
(fertilization and other actions). A postcard mailing is an inexpensive action which
could direct residents to websites and include several “what you can do” measures.
The postcard might reference the County Stormwater program website at
www.co.suffolk.ny.us/stormwater as well as the Suffolk County Water Authority
website which provides recommendations regarding the use of herbicides and
pesticides www.scwa.com/environment/fertilizer.cfm as well as other Town and
government information sources.
19. Establish educational signage at public parks and accessible lakefront locations
regarding the lake system, pollution impacts, what can be done by the community to
improve water quality, stormwater impacts, sanitary systems, pet and wildfowl impacts,
lake history and cultural resources, and all aspects of environmental awareness for Lake
Ronkonkoma.
20. Prepare mailing to all 355 EPA regulated facilities (within the zip codes of 11767,
11779, and 11755) asking for extra cooperation to prevent wastes from entering
stormwater or groundwater.
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Lake Ronkonkoma
Increase Public Access
21. Create access around the lake where feasible to increase use and foster a public
appreciation of the resource. Where a trail is not feasible, consider a boardwalk.
Incorporate educational and interpretive signage regarding lake history and
environmental awareness.
22. Use new technologies make available low-cost communication between citizens and
their community governments. The Lake Ronkonkoma Civic Association’s website is
one such example (www.lakeronkonkomacivic.org). The availability of free webmapping applications (such as www.google.com/apis/maps) allows community-based
organizations to use online maps to facilitate communications. An example of a very
useful community map is the Akron, Ohio public engineer’s website where internet
users
can
report
problems
or
make
comments
about
locations
www.uber.engineer.co.summit.oh.us/gMap/display/ez_map_editor.cfm; or the wide
variety of maps that are available such as Gypsy Map’s combination of map and
subway and bus routes for New York City http://www.gypsymaps.com. Citizens are
clearly interested in improving the future environmental quality of Lake Ronkonkoma
and thus, implementing a website where County, Town, Village or other entities can
provide location information quickly and request input or help in identifying or fixing
areas of concern might be considered. An example of this would be if the SCDPW
needs citizen input to help map and refine stormwater infrastructure for Phase II
requirements. Existing maps could be displayed and citizens could add comments
about local conditions during storms or the accuracy of even small details, such as
storm grate locations. Another possibility would be to ask residents to take pictures
during storms and post photographs on Google Maps to show the location.
23. Provide for and enhance existing recreational activities through business enterprises
facilitated by public-private partnerships such as kayak and other small boat rentals.
24. Increase and enhance public access opportunities for water-based recreation such as
fishing, sailing, canoe and kayaking, ice boating and related water-sports. Provide car
top boat access locations and maintain and enhance existing boat ramps and public
parks.
Lake Level & Flooding
25. Provide assistance to the Town of Smithtown to identify an alternative to pumping
untreated stormwater into the north end of the Great Bog. Although the bog does
provide some treatment, it would be ideal if Smithtown could proceed with the research
necessary to identify areas where the Smithtown clay layer is thinnest to increase the
feasibility of installing a recharge system below the clay layer.
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Lake Ronkonkoma
FIGURES
Lake Ronkonkoma
APPENDICES